Trial Outcomes & Findings for A Combination Study of Kadcyla (Trastuzumab Emtansine) and Capecitabine in Participants With Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Metastatic Breast Cancer (mBC) or HER2-Positive Locally Advanced/Metastatic Gastric Cancer (LA/mGC) (NCT NCT01702558)

Last Updated: 2021-01-22

Results Overview

A DLT was defined as any one of the following study treatment related toxicities: Uncomplicated Grade 4 thrombocytopenia that does not recover before Day 21; thrombocytopenia complicated with clinically significant bleeding requiring medical intervention; Grade 4 neutropenia lasting more than (\>) 7 consecutive days; febrile neutropenia with absolute neutrophil count (ANC) less than (\<) 1000 cells/millimeter cube (mm\^3); Grade greater than or equal to (\>/=) 3 diarrhea or Grade 3 hand-foot syndrome (in absence of dihydropyrimidine dehydrogenase \[DPD\] deficiency only for DL 1); any other Grade \>/=3 toxicity prohibiting start of Cycle 2; Grade 2 toxicity requiring treatment interruption for \>14 days (\>7 days for DL 1); for DL -1 only: \<14 full doses of capecitabine; Cycle 2 dose level \<100 percent (%).

Recruitment status

TERMINATED

Study phase

PHASE2

Target enrollment

182 participants

Primary outcome timeframe

Continuously during Cycle 1 (up to 3 weeks)

Results posted on

2021-01-22

Participant Flow

A total of 234 participants were screened, out of which, 182 participants were enrolled into the study. Out of the 182 enrolled participants, 3 participants were excluded from all safety and efficacy analyses because they did not sign correct Informed Consent Form (ICF).

Participant milestones

Participant milestones
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine (T-DM1) at a dose of 3.6 milligrams per kilogram (mg/kg) via intravenous (IV) infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine (Cape) at a dose level (DL) of 750 milligrams per meter squared (mg/m\^2) via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, disease progression (PD), death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (LA/mGC) Cohort 2 (DL -1): T-DM1 + Cape In Phase 1, Cohort 2 participants (with LA/mGC) received trastuzumab emtansine at a dose of 2.4 mg/kg via IV infusion on Day 1 (Day 2 of first week) of every week along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 followed by a 7-day rest period, in each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 + Cape In Phase 2, participants (with mBC) who were randomized to this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 In Phase 2, participants (with mBC) who were randomized in this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle until investigator-assessed PD, unacceptable toxicity, withdrawal of consent, death, reasons deemed by the treating physician, or study termination by the Sponsor.
Overall Study STARTED	7	5	6	81	80
Overall Study COMPLETED	3	1	1	34	38
Overall Study NOT COMPLETED	4	4	5	47	42

Reasons for withdrawal

Reasons for withdrawal
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine (T-DM1) at a dose of 3.6 milligrams per kilogram (mg/kg) via intravenous (IV) infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine (Cape) at a dose level (DL) of 750 milligrams per meter squared (mg/m\^2) via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, disease progression (PD), death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (LA/mGC) Cohort 2 (DL -1): T-DM1 + Cape In Phase 1, Cohort 2 participants (with LA/mGC) received trastuzumab emtansine at a dose of 2.4 mg/kg via IV infusion on Day 1 (Day 2 of first week) of every week along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 followed by a 7-day rest period, in each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 + Cape In Phase 2, participants (with mBC) who were randomized to this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 In Phase 2, participants (with mBC) who were randomized in this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle until investigator-assessed PD, unacceptable toxicity, withdrawal of consent, death, reasons deemed by the treating physician, or study termination by the Sponsor.
Overall Study Withdrawal by Subject	0	0	0	12	4
Overall Study Lost to Follow-up	0	0	0	3	0
Overall Study Death	4	3	3	16	20
Overall Study Safety Follow-Up less than 3 Months	0	0	2	0	0
Overall Study Study Terminated by Sponsor	0	1	0	0	1
Overall Study Other	0	0	0	16	17

Baseline Characteristics

A Combination Study of Kadcyla (Trastuzumab Emtansine) and Capecitabine in Participants With Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Metastatic Breast Cancer (mBC) or HER2-Positive Locally Advanced/Metastatic Gastric Cancer (LA/mGC)

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=5 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (LA/mGC) Cohort 2 (DL -1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 2 participants (with LA/mGC) received trastuzumab emtansine at a dose of 2.4 mg/kg via IV infusion on Day 1 (Day 2 of first week) of every week along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 followed by a 7-day rest period, in each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 + Cape n=82 Participants In Phase 2, participants (with mBC) who were randomized to this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 n=78 Participants In Phase 2, participants (with mBC) who were randomized to this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle until investigator-assessed PD, unacceptable toxicity, withdrawal of consent, death, reasons deemed by the treating physician, or study termination by the Sponsor.	Total n=178 Participants Total of all reporting groups
Age, Continuous	55.9 years STANDARD_DEVIATION 10.75 • n=5 Participants	50.8 years STANDARD_DEVIATION 7.76 • n=7 Participants	60.0 years STANDARD_DEVIATION 7.40 • n=5 Participants	53.3 years STANDARD_DEVIATION 11.69 • n=4 Participants	52.6 years STANDARD_DEVIATION 11.19 • n=21 Participants	53.2 years STANDARD_DEVIATION 11.22 • n=8 Participants
Sex: Female, Male Female	6 Participants n=5 Participants	5 Participants n=7 Participants	0 Participants n=5 Participants	81 Participants n=4 Participants	78 Participants n=21 Participants	170 Participants n=8 Participants
Sex: Female, Male Male	1 Participants n=5 Participants	0 Participants n=7 Participants	6 Participants n=5 Participants	1 Participants n=4 Participants	0 Participants n=21 Participants	8 Participants n=8 Participants
Race/Ethnicity, Customized Race: Caucasian	6 participants n=5 Participants	4 participants n=7 Participants	6 participants n=5 Participants	71 participants n=4 Participants	65 participants n=21 Participants	152 participants n=8 Participants
Race/Ethnicity, Customized Race: N/A (as per local regulation)	1 participants n=5 Participants	1 participants n=7 Participants	0 participants n=5 Participants	10 participants n=4 Participants	7 participants n=21 Participants	19 participants n=8 Participants
Race/Ethnicity, Customized Race: Black	0 participants n=5 Participants	0 participants n=7 Participants	0 participants n=5 Participants	0 participants n=4 Participants	2 participants n=21 Participants	2 participants n=8 Participants
Race/Ethnicity, Customized Race: Asian	0 participants n=5 Participants	0 participants n=7 Participants	0 participants n=5 Participants	1 participants n=4 Participants	1 participants n=21 Participants	2 participants n=8 Participants
Race/Ethnicity, Customized Race: Mixed	0 participants n=5 Participants	0 participants n=7 Participants	0 participants n=5 Participants	0 participants n=4 Participants	3 participants n=21 Participants	3 participants n=8 Participants
Race/Ethnicity, Customized Ethnicity: Hispanic/Latino	0 participants n=5 Participants	1 participants n=7 Participants	0 participants n=5 Participants	5 participants n=4 Participants	10 participants n=21 Participants	16 participants n=8 Participants
Race/Ethnicity, Customized Ethnicity: Chinese	0 participants n=5 Participants	0 participants n=7 Participants	0 participants n=5 Participants	1 participants n=4 Participants	0 participants n=21 Participants	1 participants n=8 Participants
Race/Ethnicity, Customized Ethnicity: Other	6 participants n=5 Participants	0 participants n=7 Participants	0 participants n=5 Participants	39 participants n=4 Participants	35 participants n=21 Participants	80 participants n=8 Participants
Race/Ethnicity, Customized Ethnicity: N/A (as per local regulation)	1 participants n=5 Participants	1 participants n=7 Participants	6 participants n=5 Participants	32 participants n=4 Participants	29 participants n=21 Participants	69 participants n=8 Participants
Race/Ethnicity, Customized Ethnicity: Unknown	0 participants n=5 Participants	2 participants n=7 Participants	0 participants n=5 Participants	5 participants n=4 Participants	4 participants n=21 Participants	11 participants n=8 Participants
Race/Ethnicity, Customized Ethnicity: Mixed	0 participants n=5 Participants	1 participants n=7 Participants	0 participants n=5 Participants	0 participants n=4 Participants	0 participants n=21 Participants	1 participants n=8 Participants

PRIMARY outcome

Timeframe: Continuously during Cycle 1 (up to 3 weeks)

Population: Analysis was performed on Phase 1 DLT-evaluable population for mBC cohort, which included all enrolled and treated mBC participants who did not experience any major protocol deviation and completed Cycle 1.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=5 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): Percentage of Participants With Dose-Limiting Toxicities (DLTs)	33.3 percentage of participants	0.0 percentage of participants

PRIMARY outcome

Timeframe: Continuously during Cycle 1 (up to 3 weeks)

Population: Analysis was performed on Phase 1 DLT-evaluable population for mBC cohort.

MTD was defined as the dose level for which the probability of DLT is equal to a protocol-specified target probability. A DLT was defined as any one of the following study treatment related toxicities: Uncomplicated Grade 4 thrombocytopenia that does not recover before Day 21; thrombocytopenia complicated with clinically significant bleeding requiring medical intervention; Grade 4 neutropenia lasting \>7 consecutive days; febrile neutropenia with ANC \<1000 cells/mm\^3; Grade \>/=3 diarrhea or Grade 3 hand-foot syndrome (in absence of DPD deficiency only for DL 1); any other Grade \>/=3 toxicity prohibiting start of Cycle 2; Grade 2 toxicity requiring treatment interruption for \>14 days (\>7 days for DL 1); for DL -1 only: \<14 full doses of capecitabine; Cycle 2 dose level \<100%.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=11 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): Maximum Tolerated Dose (MTD) of Capecitabine When Combined With Trastuzumab Emtansine (3.6 mg/kg Every 3 Weeks)	700 mg/m^2	—

PRIMARY outcome

Timeframe: Baseline until CR/PR, consent withdrawal, or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on Intent-to-Treat (ITT) Population, which included all participants in the randomized Phase 2 part of the study. Participants were analyzed as per the initial randomization. Participants without tumor assessment after start of study treatment were considered as non-responders.

Tumor response was assessed by the investigator according to RECIST v1.1. BOR was defined as percentage of participants with a complete response (CR) or partial response (PR) that was confirmed by repeat assessments \>/=4 weeks after initial documentation. CR was defined as the disappearance of all target lesions (TLs) and non-TLs; short axis (SA) reduction to \<10 millimeters (mm) for nodal TLs/non-TLs; and no new lesions. PR was defined as \>/=30% decrease in sum of diameters (SoD) of TLs, taking as reference the baseline SoD; no progression in non-TLs; and no new lesions. The 90% confidence Interval (CI) was computed using Clopper-Pearson approach.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Percentage of Participants With Best Overall Response (BOR) as Assessed by the Investigator According to Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST v1.1)	44.4 percentage of participants Interval 35.0 to 54.2	36.3 percentage of participants Interval 27.3 to 46.0

PRIMARY outcome

Timeframe: Continuously during 3 weeks

Population: Analysis was performed on Phase 1 DLT-evaluable population for LA/mGC cohort, which included all enrolled and treated LA/mGC participants who did not experience any major protocol deviation and completed Cycle 1.

A DLT was defined as any one of the following study treatment related toxicities: Uncomplicated Grade 4 thrombocytopenia that does not recover before Day 21; thrombocytopenia complicated with clinically significant bleeding requiring medical intervention; Grade 4 neutropenia lasting \>7 consecutive days; febrile neutropenia with ANC \<1000 cells/mm\^3; Grade \>/=3 diarrhea or Grade 3 hand-foot syndrome; any other Grade \>/=3 toxicity prohibiting start of Cycle 2; Grade 2 toxicity requiring treatment interruption for \>14 days; \<14 full doses of capecitabine; Cycle 2 dose level \<100%.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): Percentage of Participants With DLTs	0.0 percentage of participants	—

PRIMARY outcome

Timeframe: Continuously during 3 weeks

Population: Analysis was performed on Phase 1 DLT-evaluable population for LA/mGC cohort.

MTD was defined as the dose level for which the probability of DLT is equal to a protocol-specified target probability. A DLT was defined as any one of the following study treatment related toxicities: Uncomplicated Grade 4 thrombocytopenia that does not recover before Day 21; thrombocytopenia complicated with clinically significant bleeding requiring medical intervention; Grade 4 neutropenia lasting \>7 consecutive days; febrile neutropenia with ANC \<1000 cells/mm\^3; Grade \>/=3 diarrhea or Grade 3 hand-foot syndrome; any other Grade \>/=3 toxicity prohibiting start of Cycle 2; Grade 2 toxicity requiring treatment interruption for \>14 days; \<14 full doses of capecitabine; Cycle 2 dose level \<100%.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): MTD of Capecitabine When Combined With Trastuzumab Emtansine (2.4 mg/kg QW)	700 mg/m^2	—

SECONDARY outcome

Timeframe: Baseline until CR/PR, consent withdrawal, or study end whichever occurred first (up to approximately 3.5 years overall)

Population: Analysis was performed on Phase 1 DLT-evaluable population for mBC cohort.

Tumor response was assessed by the investigator according to RECIST v1.1. BOR in Phase 1 was defined as percentage of participants with a CR or PR. CR was defined as the disappearance of all TLs and non-TLs; SA reduction to \<10 mm for nodal TLs/non-TLs; and no new lesions. PR was defined as \>/=30% decrease in SoD of TLs, taking as reference the baseline SoD; no progression in non-TLs; and no new lesions.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=5 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): Percentage of Participants With BOR as Assessed by the Investigator According to RECIST v1.1	83.3 percentage of participants	100.0 percentage of participants

SECONDARY outcome

Timeframe: Pre-trastuzumab emtansine dose (0 hour [h]) on Day 1 Cycle 2; 15-30 minutes (min) after end of trastuzumab emtansine infusion (maximum infusion duration = 90 min) on Day 2 Cycle 1 and Day 1 Cycle 2 (cycle length=21 days)

Population: Phase 1 pharmacokinetic (PK) analysis population for mBC cohort; included all mBC participants receiving at least one dose of study medication during Phase 1 and had at least one reported serum/plasma result for PK. The PK analysis in mBC cohort included 1 patient who was excluded from the main safety and efficacy analyses due to ICF issues.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): Serum Concentration of Trastuzumab Emtansine Cycle 1, Post-dose	81.3 micrograms per milliliter (mcg/mL) Standard Deviation 13.3	78.6 micrograms per milliliter (mcg/mL) Standard Deviation 14.6
Phase 1 (mBC): Serum Concentration of Trastuzumab Emtansine Cycle 2, Pre-dose	1.17 micrograms per milliliter (mcg/mL) Standard Deviation 1.25	2.1 micrograms per milliliter (mcg/mL) Standard Deviation 1.49
Phase 1 (mBC): Serum Concentration of Trastuzumab Emtansine Cycle 2, Post-dose	70.5 micrograms per milliliter (mcg/mL) Standard Deviation 13.3	78.5 micrograms per milliliter (mcg/mL) Standard Deviation 14.9

SECONDARY outcome

Timeframe: Pre-trastuzumab emtansine dose (0 h) on Day 1 Cycle 2; 15-30 min after end of trastuzumab emtansine infusion (maximum infusion duration = 90 min) on Day 2 Cycle 1 and Day 1 Cycle 2 (cycle length=21 days)

Population: Analysis was performed on Phase 1 PK analysis population for mBC cohort. The PK analysis in the mBC cohort included 1 patient who was excluded from the main safety and efficacy analyses due to ICF issues.

Trastuzumab was derived from trastuzumab emtansine.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): Serum Concentration of Trastuzumab Cycle 1, Post-dose	89.1 mcg/mL Standard Deviation 24.37	92.9 mcg/mL Standard Deviation 22.13
Phase 1 (mBC): Serum Concentration of Trastuzumab Cycle 2, Pre-dose	11.8 mcg/mL Standard Deviation 13.28	14.0 mcg/mL Standard Deviation 12.53
Phase 1 (mBC): Serum Concentration of Trastuzumab Cycle 2, Post-dose	74.8 mcg/mL Standard Deviation 18.89	94.7 mcg/mL Standard Deviation 24.60

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

Cmax for Capecitabine was estimated from plasma concentration versus time data using non-compartmental methods of analysis. Reported dispersion values are for percent coefficient of variation (CV%) and not for standard deviation.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): Maximum Observed Plasma Concentration (Cmax) of Capecitabine	2990 nanograms per milliliter (ng/mL) Standard Deviation 38.4	5652 nanograms per milliliter (ng/mL) Standard Deviation 91.1

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

AUC(0-inf) is the measure of total drug exposure and is dependent on the total amount of drug absorbed. AUC(0-inf) for capecitabine was estimated from plasma concentration versus time data using non-compartmental methods of analysis. Reported dispersion values are for CV% and not for standard deviation.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): Area Under the Plasma Concentration-Time Curve From Time Zero to Infinity (AUC[0-inf]) of Capecitabine	3973 hoursnanograms per milliliter (hng/mL) Standard Deviation 38.0	5440 hoursnanograms per milliliter (hng/mL) Standard Deviation 57.7

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

Plasma terminal half-life is the time measured for the plasma drug concentration to decrease by one half during the elimination phase of the drug. t1/2 for capecitabine was estimated from plasma concentration versus time data using non-compartmental methods of analysis. Reported dispersion values are for CV% and not for standard deviation.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): Plasma Terminal Half-Life (t1/2) of Capecitabine	0.70 hours Standard Deviation 131.9	0.39 hours Standard Deviation 38.8

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

5-fluorouracil is a metabolite of capecitabine. Cmax for 5-fluorouracil was estimated from plasma concentration versus time data using non-compartmental methods of analysis. Reported dispersion values are for CV% and not for standard deviation.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): Cmax of 5-Fluorouracil (Metabolite of Capecitabine)	148 ng/mL Standard Deviation 49.9	143 ng/mL Standard Deviation 45.6

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

5-fluorouracil is a metabolite of capecitabine. AUC(0-inf) is the measure of total drug exposure and is dependent on the total amount of drug absorbed. AUC(0-inf) for 5-fluorouracil was estimated from plasma concentration versus time data using non-compartmental methods of analysis. Reported dispersion values are for CV% and not for standard deviation.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): AUC(0-inf) of 5-Fluorouracil (Metabolite of Capecitabine)	257 h*ng/mL Standard Deviation 49.9	244 h*ng/mL Standard Deviation 38.2

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

5-fluorouracil is a metabolite of capecitabine. Plasma terminal half-life is the time measured for the plasma drug concentration to decrease by one half during the elimination phase of the drug. t1/2 for 5-fluorouracil was estimated from plasma concentration versus time data using non-compartmental methods of analysis. Reported dispersion values are for CV% and not for standard deviation.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (mBC): t1/2 of 5-Fluorouracil (Metabolite of Capecitabine)	0.63 hours Standard Deviation 39.5	0.64 hours Standard Deviation 18.3

SECONDARY outcome

Timeframe: Baseline until first documentation of confirmed PR or CR, whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population. Only participants with a BOR of CR or PR were included in the analysis.

Tumor response was assessed by the investigator according to RECIST v1.1. TTR was defined as the time (in months) from randomization to first documentation of confirmed PR or CR (whichever occurred first). CR was defined as the disappearance of all TLs and non-TLs; SA reduction to \<10 mm for nodal TLs/non-TLs; and no new lesions. PR was defined as \>/=30% decrease in SoD of TLs, taking as reference the baseline SoD; no progression in non-TLs; and no new lesions.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=36 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=29 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Time to Response (TTR) as Assessed by the Investigator According to RECIST v1.1	2.10 months Interval 1.2 to 10.8	2.10 months Interval 1.9 to 8.0

SECONDARY outcome

Timeframe: From the documentation of response until PD, death, consent withdrawal, or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population. Only participants with a BOR of CR or PR were included in the analysis.

Tumor response was assessed by the investigator according to RECIST v1.1. DoR was defined as the time (in months) from the date of first recorded PR/CR until the date of PD or death from any cause. CR: the disappearance of all TLs and non-TLs; SA reduction to \<10 mm for nodal TLs/non-TLs; and no new lesions. PR: \>/=30% decrease in SoD of TLs, taking as reference the baseline SoD; no progression in non-TLs; and no new lesions. PD: \>/=20% relative increase with \>/=5 mm of absolute increase in the SoD, taking as reference the smallest SoD recorded since treatment started; 1 or more new lesion(s); and/or unequivocal progression of non-TLs. Participants with no documented PD after CR/PR were censored at the time of last tumor assessment. Participants without post-baseline tumor assessment were censored at randomization plus 1 day. The median DOR and 90% CI were estimated using Kaplan-Meier method.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=36 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=29 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Duration of Response (DoR) as Assessed by the Investigator According to RECIST v1.1	11.30 months Interval 8.61 to Upper limit of 90% CI could not be calculated due to insufficient number of participants who had an event.	12.22 months Interval 8.84 to 15.97

SECONDARY outcome

Timeframe: Baseline until PD, consent withdrawal, or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population.

Tumor response was assessed by the investigator according to RECIST v1.1. PD was defined as \>/=20% relative increase with \>/=5 mm of absolute increase in the SoD, taking as reference the smallest SoD recorded since treatment started; 1 or more new lesion(s); and/or unequivocal progression of non-TLs.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Percentage of Participants With PD as Assessed by the Investigator According to RECIST v1.1	64.2 percentage of participants	70.0 percentage of participants

SECONDARY outcome

Timeframe: Baseline until PD, consent withdrawal, or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population.

Tumor response was assessed by the investigator according to RECIST v1.1. TTP was defined as the time (in months) from randomization to the first occurrence of PD. PD was defined as \>/=20% relative increase with \>/=5 mm of absolute increase in the SoD, taking as reference the smallest SoD recorded since treatment started; 1 or more new lesion(s); and/or unequivocal progression of non-TLs. Participants with no documented PD at the time of study end (including participants who died before PD) or who were lost to follow-up were censored on the date of the last tumor assessment. The median TTP and 90% CI was estimated using Kaplan-Meier method.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Time to Progression (TTP) as Assessed by the Investigator According to RECIST v1.1	10.38 months Interval 7.85 to 12.91	10.32 months Interval 7.56 to 13.27

SECONDARY outcome

Timeframe: Baseline until treatment failure, consent withdrawal, or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population.

Treatment failure was defined as occurrence of any of the following event while on treatment: PD, death, withdrawal due to adverse event (AE) or laboratory abnormality, or refusal of treatment. PD as assessed by the investigator according to RECIST v1.1 was defined as \>/=20% relative increase with \>/=5 mm of absolute increase in the SoD, taking as reference the smallest SoD recorded since treatment started; 1 or more new lesion(s); and/or unequivocal progression of non-TLs.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Percentage of Participants With Treatment Failure as Assessed by the Investigator According to RECIST v1.1	77.8 percentage of participants	83.8 percentage of participants

SECONDARY outcome

Timeframe: Baseline until treatment failure, consent withdrawal, or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population.

TTF was defined as the time (in months) from randomization until treatment failure (PD, death, withdrawal due to AE or laboratory abnormality, or refusal of treatment). PD as assessed by the investigator according to RECIST v1.1 was defined as \>/=20% relative increase with \>/=5 mm of absolute increase in the SoD, taking as reference the smallest SoD recorded since treatment started; 1 or more new lesion(s); and/or unequivocal progression of non-TLs. Participants who did not experience any of the above events while on study were censored on the date of their last tumor assessment. The median TTF and 90% CI was estimated using Kaplan-Meier method.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Time to Treatment Failure (TTF) as Assessed by the Investigator According to RECIST v1.1	9.86 months Interval 7.62 to 10.68	7.66 months Interval 6.54 to 10.68

SECONDARY outcome

Timeframe: Baseline until PD, death from any cause, consent withdrawal, or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Percentage of Participants With PD as Assessed by the Investigator According to RECIST v1.1 or Death From Any Cause	67.9 percentage of participants	73.8 percentage of participants

SECONDARY outcome

Timeframe: Baseline until PD, death from any cause, consent withdrawal, or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population.

Tumor response was assessed by the investigator according to RECIST v1.1. PFS was defined as the time (in months) from randomization until the first documented PD or death from any cause, whichever occurred first. PD was defined as \>/=20% relative increase with \>/=5 mm of absolute increase in the SoD, taking as reference the smallest SoD recorded since treatment started; 1 or more new lesion(s); and/or unequivocal progression of non-TLs. Participants with no PFS events were censored on the date of the last tumor assessment. Participants without post-baseline tumor assessment were censored at randomization plus 1 day. The median PFS and 90% CI was estimated using Kaplan-Meier method.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Progression-Free Survival (PFS) as Assessed by the Investigator According to RECIST v1.1	10.15 months Interval 7.85 to 12.55	9.82 months Interval 7.46 to 13.08

SECONDARY outcome

Timeframe: Baseline until clinical benefit response, consent withdrawal, or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population.

The clinical benefit was defined as a confirmed response of CR, PR, or stable disease (SD) that lasted for at least 6 months. Tumor response was assessed by the investigator according to RECIST v1.1. CR: the disappearance of all TLs and non-TLs; SA reduction to \<10 mm for nodal TLs/non-TLs; and no new lesions. PR: \>/=30% decrease in SoD of TLs, taking as reference the baseline SoD; no progression in non-TLs; and no new lesions. PD: \>/=20% relative increase with \>/=5 mm of absolute increase in the SoD, taking as reference the smallest SoD recorded since treatment started; 1 or more new lesion(s); and/or unequivocal progression of non-TLs. SD: neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD, taking as reference the smallest SoD on study. The 90% CI was computed using Clopper-Pearson approach.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Percentage of Participants With Clinical Benefit as Assessed by the Investigator According to RECIST v1.1	66.7 percentage of participants Interval 57.1 to 75.3	62.5 percentage of participants Interval 52.7 to 71.6

SECONDARY outcome

Timeframe: Baseline until death or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Percentage of Participants Who Died of Any Cause	22.2 percentage of participants	26.3 percentage of participants

SECONDARY outcome

Timeframe: Baseline until death or study end whichever occurred first (up to approximately 2.5 years overall)

Population: Analysis was performed on ITT Population.

OS was defined as the time (in months) from randomization until death from any cause. Participants who were alive at the time of data cut-off were censored on the date of the last follow-up assessment. Participants who were lost to follow-up were censored as having no event (alive) on the date of last contact. The median OS and 90% CI was estimated using Kaplan-Meier method, which use the patients at risk as denominator rather than the whole number of patients.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=81 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=80 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 2 (mBC): Overall Survival (OS)	NA months Median and 90% CI could not be calculated due to insufficient number of participants who had an event.	24.71 months Interval 24.28 to Upper limit of 90% CI could not be calculated due to insufficient number of participants who had an event.

SECONDARY outcome

Timeframe: Baseline until CR/PR, consent withdrawal, or study end whichever occurred first (up to approximately 1.5 years overall)

Population: Analysis was performed on Phase 1 DLT-evaluable population for LA/mGC cohort.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): Percentage of Participants With BOR as Assessed by the Investigator According to RECIST v1.1	83.3 percentage of participants	—

SECONDARY outcome

Population: Analysis was performed on Phase 1 PK analysis population for LA/mGC cohort.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): Serum Concentration of Trastuzumab Emtansine Cycle 1, Post-dose	30.1 mcg/mL Standard Deviation 14.5	—
Phase 1 (LA/mGC): Serum Concentration of Trastuzumab Emtansine Cycle 2, Pre-dose	10.1 mcg/mL Standard Deviation 5.85	—
Phase 1 (LA/mGC): Serum Concentration of Trastuzumab Emtansine Cycle 2, Post-dose	46.4 mcg/mL Standard Deviation 7.74	—

SECONDARY outcome

Population: Analysis was performed on Phase 1 PK analysis population for LA/mGC cohort.

Trastuzumab was derived from trastuzumab emtansine.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): Serum Concentration of Trastuzumab Cycle 1, Post-dose	33.1 mcg/mL Standard Deviation 15.98	—
Phase 1 (LA/mGC): Serum Concentration of Trastuzumab Cycle 2, Pre-dose	18.5 mcg/mL Standard Deviation 7.57	—
Phase 1 (LA/mGC): Serum Concentration of Trastuzumab Cycle 2, Post-dose	57.6 mcg/mL Standard Deviation 13.55	—

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

Population: Analysis was performed on Phase 1 PK analysis population for LA/mGC cohort.

Cmax for capecitabine was estimated from plasma concentration versus time data using non-compartmental methods of analysis. Reported dispersion values are for CV% and not for standard deviation.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): Cmax of Capecitabine	4925 ng/mL Standard Deviation 36.3	—

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

Population: Analysis was performed on Phase 1 PK analysis population for LA/mGC cohort.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): AUC(0-inf) of Capecitabine	5131 h*ng/mL Standard Deviation 24.6	—

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

Population: Analysis was performed on Phase 1 PK analysis population for LA/mGC cohort.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): t1/2 of Capecitabine	0.65 hours Standard Deviation 34.5	—

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

Population: Analysis was performed on Phase 1 PK analysis population for LA/mGC cohort.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): Cmax of 5-Fluorouracil (Metabolite of Capecitabine)	137 ng/mL Standard Deviation 24.3	—

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

Population: Analysis was performed on Phase 1 PK analysis population for LA/mGC cohort.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): AUC(0-inf) of 5-Fluorouracil (Metabolite of Capecitabine)	213 h*ng/mL Standard Deviation 16.2	—

SECONDARY outcome

Timeframe: Pre-capecitabine dose (0 h) and 0.5, 1, 1.5, 2, 2.5, 4, and 6 h post-capecitabine dose on Day 1 Cycle 1

Population: Analysis was performed on Phase 1 PK analysis population for LA/mGC cohort.

Outcome measures

Outcome measures
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=6 Participants In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.
Phase 1 (LA/mGC): t1/2 of 5-Fluorouracil (Metabolite of Capecitabine)	0.83 hours Standard Deviation 17.0	—

Adverse Events

Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape

Serious events: 0 serious events

Other events: 7 other events

Deaths: 4 deaths

Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape

Serious events: 2 serious events

Other events: 5 other events

Deaths: 3 deaths

Phase 1 (LA/mGC) Cohort 2 (DL -1): T-DM1 + Cape

Serious events: 4 serious events

Other events: 6 other events

Deaths: 3 deaths

Phase 2 (mBC): T-DM1 + Cape

Serious events: 11 serious events

Other events: 75 other events

Deaths: 18 deaths

Phase 2 (mBC): T-DM1

Serious events: 10 serious events

Other events: 64 other events

Deaths: 21 deaths

Serious adverse events

Serious adverse events
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 participants at risk In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=5 participants at risk In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (LA/mGC) Cohort 2 (DL -1): T-DM1 + Cape n=6 participants at risk In Phase 1, Cohort 2 participants (with LA/mGC) received trastuzumab emtansine at a dose of 2.4 mg/kg via IV infusion on Day 1 (Day 2 of first week) of every week along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 followed by a 7-day rest period, in each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 + Cape n=82 participants at risk In Phase 2, participants (with mBC) who were randomized to this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 n=78 participants at risk In Phase 2, participants (with mBC) who were randomized to this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle until investigator-assessed PD, unacceptable toxicity, withdrawal of consent, death, reasons deemed by the treating physician, or study termination by the Sponsor.
Musculoskeletal and connective tissue disorders Muscular weakness	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Pathological fracture	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Brain oedema	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Cerebral cyst	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Radiation necrosis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Cardiac disorders Myocardial infarction	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Diarrhoea	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Device related sepsis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Tumour haemorrhage	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Renal and urinary disorders Renal colic	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Surgical and medical procedures Tumour excision	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Abdominal pain	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	2.4% 2/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Colitis ischaemic	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Intestinal haematoma	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Mesenteric vein thrombosis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Vomiting	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Gastroenteritis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Bacterial sepsis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Device related infection	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Upper respiratory tract infection	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Urinary tract infection	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Wound sepsis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Renal and urinary disorders Haematuria	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Renal and urinary disorders Anuria	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Pleural effusion	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Pleurisy	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Pulmonary embolism	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Hepatobiliary disorders Cholecystitis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Hepatobiliary disorders Hepatocellular injury	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Diabetes mellitus	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Hyperglycaemia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Sciatica	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Blood and lymphatic system disorders Thrombocytopenia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Fracture displacement	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Hepatic enzyme increased	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Reproductive system and breast disorders Uterine polyp	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.

Other adverse events

Other adverse events
Measure	Phase 1 (mBC) Cohort 1 (DL 1): T-DM1 + Cape n=7 participants at risk In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 750 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (mBC) Cohort 1 (DL -1): T-DM1 + Cape n=5 participants at risk In Phase 1, Cohort 1 participants (with mBC) received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion (on Day 1 \[on Day 2 for Cycle 1\] of each 21-day cycle) along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 1 (LA/mGC) Cohort 2 (DL -1): T-DM1 + Cape n=6 participants at risk In Phase 1, Cohort 2 participants (with LA/mGC) received trastuzumab emtansine at a dose of 2.4 mg/kg via IV infusion on Day 1 (Day 2 of first week) of every week along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 followed by a 7-day rest period, in each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 + Cape n=82 participants at risk In Phase 2, participants (with mBC) who were randomized to this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle along with capecitabine at a dose level of 700 mg/m\^2 via tablet orally twice daily on Days 1-14 of each 21-day cycle until unacceptable toxicity, withdrawal of consent, PD, death, reasons deemed by the treating physician, or study termination by the sponsor.	Phase 2 (mBC): T-DM1 n=78 participants at risk In Phase 2, participants (with mBC) who were randomized to this group received trastuzumab emtansine at a dose of 3.6 mg/kg via IV infusion on Day 1 of each 21-day cycle until investigator-assessed PD, unacceptable toxicity, withdrawal of consent, death, reasons deemed by the treating physician, or study termination by the Sponsor.
Gastrointestinal disorders Ascites	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Melaena	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Nausea	42.9% 3/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	80.0% 4/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	50.0% 3/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	32.9% 27/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	23.1% 18/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Diarrhoea	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	60.0% 3/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	8.5% 7/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	9.0% 7/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Constipation	42.9% 3/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	80.0% 4/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	66.7% 4/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	9.8% 8/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	10.3% 8/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Gingival bleeding	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	60.0% 3/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Vomiting	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	19.5% 16/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	10.3% 8/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Abdominal pain upper	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	60.0% 3/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	7.3% 6/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.4% 5/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Dry mouth	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	3.7% 3/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	7.7% 6/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Toothache	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Abdominal distension	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Abdominal pain	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	8.5% 7/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	2.6% 2/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Haematochezia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Rectal haemorrhage	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Anal fissure	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Anal haemorrhage	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Chapped lips	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Dental caries	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Dyspepsia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Dysphagia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Eructation	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Flatulence	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Frequent bowel movements	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Gastrooesophageal reflux disease	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Gingival pain	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Glossodynia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Haemorrhoidal haemorrhage	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Hypoaesthesia oral	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Arthralgia	42.9% 3/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	13.4% 11/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	11.5% 9/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Back pain	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	4.9% 4/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	5.1% 4/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Muscle spasms	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.1% 5/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Muscular weakness	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Musculoskeletal pain	42.9% 3/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	4.9% 4/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	7.7% 6/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Myalgia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	8.5% 7/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	2.6% 2/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Stomatitis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	3.7% 3/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.4% 5/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Gastric haemorrhage	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Pain in extremity	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	3.7% 3/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.4% 5/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Bone pain	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Joint stiffness	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Joint swelling	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Musculoskeletal chest pain	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Neck pain	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Joint range of motion decreased	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Muscle twitching	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Musculoskeletal stiffness	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Arthritis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Coccydynia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Flank pain	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Groin pain	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Limb mass	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Osteonecrosis of jaw	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Tendonitis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Musculoskeletal and connective tissue disorders Weight bearing difficulty	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Non-cardiac chest pain	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Fatigue	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	66.7% 4/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	12.2% 10/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	14.1% 11/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Asthenia	42.9% 3/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.7% 17/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	19.2% 15/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Chills	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.4% 5/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Gait disturbance	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Peripheral swelling	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Pain	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Pyrexia	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	15.9% 13/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	19.2% 15/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Mucosal inflammation	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Oedema peripheral	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	3.7% 3/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	5.1% 4/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Influenza like illness	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Malaise	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Catheter site rash	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Mucosal dryness	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Headache	57.1% 4/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	60.0% 3/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	9.8% 8/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.4% 5/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Neuropathy peripheral	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	2.4% 2/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	5.1% 4/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Dizziness	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Migraine	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Balance disorder	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Hypoaesthesia	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Amnesia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Aphonia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Hemiparesis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Neuralgia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Neurotoxicity	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Seizure	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Tremor	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Vocal cord paralysis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Paraesthesia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.1% 5/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	2.6% 2/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Epistaxis	57.1% 4/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	60.0% 3/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	18.3% 15/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	12.8% 10/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Cough	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.1% 5/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	7.7% 6/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Rhinorrhoea	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	60.0% 3/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Haemoptysis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Nasal ulcer	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Oropharyngeal pain	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Pleural effusion	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Rhinitis allergic	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Sleep apnoea syndrome	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Palmar-plantar erythrodysaesthesia syndrome	42.9% 3/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.7% 17/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	2.6% 2/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Rash macular	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	60.0% 3/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Dry skin	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Rash	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Pruritus	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Macule	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Acne	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Alopecia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.4% 5/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Blister	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Dermatitis acneiform	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Ecchymosis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Eczema	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Ingrowing nail	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Nail discolouration	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Onycholysis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Rash erythematous	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Rash maculo-papular	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Rash pruritic	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
General disorders Impaired healing	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Skin discolouration	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Skin mass	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Skin ulcer	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Swelling face	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Influenza	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Urinary tract infection	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Viral upper respiratory tract infection	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Conjunctivitis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	5.1% 4/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Cystitis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Herpes zoster	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Pharyngitis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Pneumonia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Sinusitis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Ear infection	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Eye infection	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Folliculitis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Fungal skin infection	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Furuncle	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Laryngitis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Localised infection	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Oral candidiasis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Paronychia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Aspartate aminotransferase increased	57.1% 4/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	32.9% 27/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	39.7% 31/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Platelet count decreased	57.1% 4/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	14.6% 12/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 13/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Alanine aminotransferase increased	57.1% 4/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	24.4% 20/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	30.8% 24/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Blood bilirubin increased	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	7.3% 6/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	5.1% 4/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Blood lactate dehydrogenase increased	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	11.0% 9/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	12.8% 10/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Gamma-glutamyltransferase increased	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	9.8% 8/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.5% 16/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Aspartate aminotransferase	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Transaminases increased	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Weight decreased	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Hepatobiliary disorders Hyperbilirubinaemia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Hepatobiliary disorders Hepatocellular injury	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Hypomagnesaemia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Hypokalaemia	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	40.0% 2/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	4.9% 4/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	5.1% 4/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Decreased appetite	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	12.2% 10/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	14.1% 11/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Cell death	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Dry eye	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Lacrimation increased	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	7.3% 6/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	3.8% 3/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Ocular hyperaemia	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Eye haemorrhage	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Eye pain	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Blepharospasm	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Blindness	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Keratitis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Pterygium	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Retinal ischaemia	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Vision blurred	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Eye disorders Visual impairment	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Blood and lymphatic system disorders Thrombocytopenia	42.9% 3/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	80.0% 4/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	42.7% 35/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	26.9% 21/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Blood and lymphatic system disorders Neutropenia	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	15.9% 13/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	7.7% 6/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Blood and lymphatic system disorders Anaemia	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	66.7% 4/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	11.0% 9/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 13/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Contusion	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	60.0% 3/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Procedural headache	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Arthropod sting	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Eye contusion	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Skin abrasion	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Skin injury	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Psychiatric disorders Insomnia	28.6% 2/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Psychiatric disorders Depression	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Psychiatric disorders Affect lability	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Psychiatric disorders Confusional state	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Ear and labyrinth disorders Tinnitus	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Ear and labyrinth disorders Deafness unilateral	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Ear and labyrinth disorders Middle ear effusion	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Vascular disorders Flushing	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Vascular disorders Bloody discharge	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Vascular disorders Hot flush	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Vascular disorders Thrombosis	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Cardiac disorders Cardiac failure	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Congenital, familial and genetic disorders Gilbert's syndrome	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Endocrine disorders Cushingoid	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Immune system disorders Hypersensitivity	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Skin papilloma	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Renal and urinary disorders Dysuria	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Reproductive system and breast disorders Breast mass	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Surgical and medical procedures Skin lesion excision	14.3% 1/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations White blood cell count decreased	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Blood alkaline phosphatase increased	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.1% 5/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	19.2% 15/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Blood creatinine increased	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations International normalised ratio increased	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Neutrophil count decreased	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Dyspnoea	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	2.4% 2/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	5.1% 4/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Nasal inflammation	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Productive cough	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Rales	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Respiratory, thoracic and mediastinal disorders Sinus disorder	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Onychoclasis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Erythema	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Erythema multiforme	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Rash papular	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Spider naevus	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Skin and subcutaneous tissue disorders Telangiectasia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Oral herpes	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Pleural infection	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Skin infection	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Streptococcal infection	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Hypoalbuminaemia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Hyperkalaemia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Hyponatraemia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Hypoproteinaemia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Blood and lymphatic system disorders Lymphadenopathy	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Dysgeusia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Syncope	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Peripheral sensory neuropathy	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Nervous system disorders Restless legs syndrome	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Cardiac disorders Tachycardia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.2% 1/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.4% 5/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Cardiac disorders Sinus tachycardia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Ear and labyrinth disorders Vertigo	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	33.3% 2/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Periorbital haematoma	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Injury, poisoning and procedural complications Thermal burn	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Surgical and medical procedures Tooth extraction	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Surgical and medical procedures Tumour excision	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Vascular disorders Deep vein thrombosis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Vascular disorders Hypertension	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Hepatobiliary disorders Jaundice	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Reproductive system and breast disorders Benign prostatic hyperplasia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	16.7% 1/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Gastrointestinal disorders Gastritis	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	5.1% 4/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Infections and infestations Upper respiratory tract infection	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.1% 5/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	1.3% 1/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Investigations Liver palpable	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	20.0% 1/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.
Metabolism and nutrition disorders Hyperglycaemia	0.00% 0/7 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/5 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	0.00% 0/6 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	3.7% 3/82 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.	6.4% 5/78 • Phase 1: Baseline up to 42 days after last dose (up to approximately 1.5 years overall); Phase 2: Baseline up to 42 days after last dose (up to approximately 2.5 years overall) Safety population included all participants who received \>/=1 dose of study drug. Participants were analyzed as per actual treatment received. In Phase 2, out of 161 participants, 1 participant was randomized in error (did not receive any treatment) and was excluded from safety analysis and 1 participant who was randomized to T-DM1 alone Arm received Capecitabine throughout study and was counted in T-DM1+Cape Arm.

Additional Information

Medical Communications

Hoffmann-La Roche

Phone: 800 821-8590

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee The Study being conducted under this Agreement is part of the Overall Study. Investigator is free to publish in reputable journals or to present at professional conferences the results of the Study, but only after the first publication or presentation that involves the Overall Study. The Sponsor may request that Confidential Information be deleted and/or the publication be postponed in order to protect the Sponsor's intellectual property rights.
Publication restrictions are in place

Restriction type: OTHER