Trial Outcomes & Findings for Feasibility Study of FLASH Radiotherapy for the Treatment of Symptomatic Bone Metastases (NCT NCT04592887)

Last Updated: 2024-07-31

Results Overview

Number of participants with total time on table under one hour. The investigational site staff will measure the time for participant set-up and positioning on the treatment couch, imaging and FLASH treatment delivery. The workflow feasibility outcome measure is met for an individual subject if total time on table is measured as less than one hour. The outcome measure data table provides the mean and full range of time on table (as measured in minutes) for the 10 participants. The participant with a treatment time of 33 minutes received treatment to two separate metastatic sites; remaining 9 participants received treatment to a single metastatic site.

Recruitment status

COMPLETED

Study phase

Target enrollment

10 participants

Primary outcome timeframe

Will be assessed on day of treatment delivery which occurs within 3 weeks of subject enrollment.

Results posted on

2024-07-31

Participant Flow

Participant milestones

Participant milestones
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Overall Study STARTED	10
Overall Study COMPLETED	10
Overall Study NOT COMPLETED	0

Reasons for withdrawal

Withdrawal data not reported

Baseline Characteristics

Feasibility Study of FLASH Radiotherapy for the Treatment of Symptomatic Bone Metastases

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) n=10 Participants FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Age, Customized Participant age at least 18 year	10 Participants n=5 Participants
Sex: Female, Male Female	5 Participants n=5 Participants
Sex: Female, Male Male	5 Participants n=5 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	0 Participants n=5 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	10 Participants n=5 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=5 Participants
Race (NIH/OMB) Asian	0 Participants n=5 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=5 Participants
Race (NIH/OMB) Black or African American	0 Participants n=5 Participants
Race (NIH/OMB) White	10 Participants n=5 Participants
Race (NIH/OMB) More than one race	0 Participants n=5 Participants
Race (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants
Region of Enrollment United States	10 participants n=5 Participants

PRIMARY outcome

Timeframe: Will be assessed on day of treatment delivery which occurs within 3 weeks of subject enrollment.

Outcome measures

Outcome measures
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) n=10 Participants FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Workflow Feasibility	15.8 minutes Interval 11.0 to 33.0

PRIMARY outcome

Timeframe: Will be assessed within 4 weeks of subject enrollment.

Number of participants whose treatment was delayed by more than 7 business days from simulation to treatment when related to the investigational device (excluding delays due to patient or facility factors not related to study treatment). The investigational site staff will measure the number of days delay in time to treatment due to problems involving the investigational device. The workflow feasibility outcome measure is met for an individual subject if the delay is measured as less than 7 days. The outcome measure data table provides the mean and full range days of treatment delay for the 10 participants.

Outcome measures

Outcome measures
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) n=10 Participants FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Workflow Feasibility	0 days Interval 0.0 to 0.0

PRIMARY outcome

Timeframe: Assessed from start of treatment until subject death or lost to follow-up, up to 17.8 months

Toxicities that are possibly, probably, or definitely related to FLASH radiotherapy. Toxicities will be classified per CTCAE version 5.0. The outcome measure data table summarizes the total number of adverse events possibly, probably, definitely related to treatment that were reported in the 10 participant cohort. Eleven adverse events were grade 1 and one adverse event was grade 2, as classified by CTCAE version 5.0.

Outcome measures

Outcome measures
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) n=10 Participants FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Assessment of Radiation-related Toxicities That Are Possibly, Probably, or Definitely Related to FLASH Radiotherapy. Grade 1 adverse events	11 adverse events related to treatment
Assessment of Radiation-related Toxicities That Are Possibly, Probably, or Definitely Related to FLASH Radiotherapy. Grade 2 adverse events	1 adverse events related to treatment

SECONDARY outcome

Timeframe: At 3 month follow up

Population: The outcome measures data table details the percentage of pain response rate (in the categories of response described above) for 12 treated sites involving 10 participants.

Percentage of treated sites achieving pain relief as measured using patient reported outcome questionnaires (Brief Pain Inventory Questionnaire, Treated Sites Pain Questionnaire). Categories of pain relief included complete, partial, stable or progressive response. Complete response (CR) = no pain at 3 months Partial response (PR) = an average pain score that is ≥2 points lower than initial Stable disease (SD) = an average pain score that is ±1 point change from initial Progressive disease (PD) = an average pain score that is ≥2 points higher than initial

Outcome measures

Outcome measures
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) n=12 Treated Sites FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Pain Relief Complete Response	50 Percentage of treated sites
Pain Relief Partial Response	16.7 Percentage of treated sites
Pain Relief Stable Response	25 Percentage of treated sites
Pain Relief Progressive Reponse	8 Percentage of treated sites

SECONDARY outcome

Timeframe: First 10 days post FLASH treatment

Pain was assessed by patient reported validated 10 point pain flare questionnaire. Pain flare is defined as either of the following: A) a minimum of a two-point increase in the worst pain score for the treated site without a reduction in analgesic intake; or B) a 25% or greater increase in analgesic intake based on daily oral morphine equivalence without a reduction in the worst pain score.

Outcome measures

Outcome measures
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) n=10 Participants FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Number of Participants Who Experienced a Pain Flare.	4 Participants

SECONDARY outcome

Timeframe: Within 10 days after treatment.

Population: Four out of the 10 participants experienced a pain flare. Two of these 4 participants met criteria B) whose use of pain medication in the first 10 days after treatment met the endpoint for pain flare.

Use of pain medication by study participant during days 1-10 following FLASH treatment was collected as it constituted one of the defining criteria (criteria B) for the pain flare outcome measure. Pain flare is defined as either of the following: A) a minimum of a two-point increase in the worst pain score for the treated site without a reduction in analgesic intake; or B) a 25% or greater increase in analgesic intake based on daily oral morphine equivalence without a reduction in the worst pain score.

Outcome measures

Outcome measures
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) n=10 Participants FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Number of Participants With Increased Use of Pain Medication in First 10 Days Post FLASH Treatment	2 Participants

Adverse Events

FLASH Radiotherapy for Painful Bone Metastasis(-es)

Serious events: 7 serious events

Other events: 10 other events

Deaths: 6 deaths

Serious adverse events

Serious adverse events
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) n=10 participants at risk FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Musculoskeletal and connective tissue disorders Chest Wall Pain	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Psychiatric disorders Confusion	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Disease Progression	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Dyspnea	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Fever	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Hepatobiliary disorders Hepatic Failure	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Hypoxia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Infections and infestations Lung Infection	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Nausea	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Pain in Extremity	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Pleural Effusion	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Pulmonary Edema	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Cardiac disorders Pulmonary Disease	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Skin Infection	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Urinary Tract Obstruction	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Vomiting	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Blood and lymphatic system disorders Anemia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Anorexia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.

Other adverse events

Other adverse events
Measure	FLASH Radiotherapy for Painful Bone Metastasis(-es) n=10 participants at risk FLASH Radiotherapy: FLASH radiotherapy is radiation treatment delivered at ultra-high dose rates compared to conventional radiation treatment.
Skin and subcutaneous tissue disorders Treatment Related Skin Hyperpigmentation	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Treatment Related Pruritis	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Treatment Related Edema limb	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Treatment Related Pain in extremity	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Treatment Related Skin discoloration	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Treatment Related Fatigue	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Treatment Related Erythema	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Abdominal Pain	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Activated Partial Thromboplastin Time Prolonged	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Psychiatric disorders Agitation	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Nervous system disorders Akathisia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Alanine aminotransferase increased	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Alkaline Phosphatase Increased	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Alopecia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Blood and lymphatic system disorders Anemia	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Injury, poisoning and procedural complications Ankle fracture	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations ANC Decreased	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Anorexia	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Psychiatric disorders Anxiety	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Arthralgia	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Ascites	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Aspartate aminotransferase increased	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Atelectasis	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Cardiac disorders Atrial Fibrillation	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Back Pain	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Blood Bicarbonate Decreased	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Blood bicarbonate Increased	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Blood Bilirubin Increased	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Blood Lactate Dehydrogenase Increased	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Eye disorders Blurred Vision	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Bone Pain	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Injury, poisoning and procedural complications Bruising	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Cardiac Troponin Increased	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Chest Wall Pain	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Chills	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Chronic Kidney Disease	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Colitis	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Nervous system disorders Concentration Impairment	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Psychiatric disorders Confusion	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Constipation	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Cough	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Creatinine Increased	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Dehydration	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Dental Caries	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Psychiatric disorders Depression	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Diarrhea	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Blood and lymphatic system disorders Disseminated Intravascular Coagulation	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Nervous system disorders Dizziness	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Dry Mouth	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Dry skin	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Dysphagia	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Dyspnea	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Dysuria	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Ear and labyrinth disorders Ear Pain	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Edema Face	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Edema Limb	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Ejection Fraction Decreased	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Epistaxis	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Infections and infestations Epstein-Barr Virus Infection	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Eye disorders Eye Pain	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Facial Asymmetry	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Injury, poisoning and procedural complications Fall	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Fatigue	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Fecal Incontinence	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Fever	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Fibrinogen	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Flank Pain	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Flatulence	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Flu-like Symptoms	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Vascular disorders Flushing	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Injury, poisoning and procedural complications Fracture	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Gait Disturbance	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Gastroesophageal Reflux disease	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Gastrointestinal disorders, other - mouth sores	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders General Disorders & Administration Site Conditions, other- Chest tightness	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Generalized Muscle Weakness	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Nervous system disorders Headache	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Vascular disorders Hematoma (Perinephric)	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Hematuria	50.0% 5/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hypercalcemia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hyperglycemia	90.0% 9/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Hyperhidrosis	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hyperkalemia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Vascular disorders Hypertension	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hypertriglyceridemia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hyperuricemia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hypophosphatemia	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hypoalbuminemia	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hypocalcemia	70.0% 7/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hypoglycemia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hypokalemia	50.0% 5/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hypomagnesemia	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Hyponatremia	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Vascular disorders Hypotension	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Endocrine disorders Hypothyroidism	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Hypoxia	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Ileus	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Infections and infestations Infections and infestations - Other, COVID-19	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Infections and infestations Infections and infestations - Other, Strep throat	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Injury, poisoning and procedural complications Injury, poisoning and procedural complications, other- Pain/injury to side	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations INR Increased	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Psychiatric disorders Insomnia	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Joint Effusion	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Joint Range of Motion Decreased	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Localized Edema	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Infections and infestations Lung Infection	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Lymphocyte count decreased	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Malaise	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Reproductive system and breast disorders Menorrhagia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Morbilliform rash	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Muscle Weakness Lower Limb	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Muscle Weakness Upper Limb	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Musculoskeletal and connective tissue disorder - Other, clavical pain	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Musculoskeletal and connective tissue disorders, other- Back weakness	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Neck pain	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Myalgia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Cardiac disorders Myocardial Infarction	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Nasal Congestion	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Nausea	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Neoplasms benign, malignant and unspecified - Other, Baker's Cyst	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Neutrophil count decreased	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Reproductive system and breast disorders Nipple Deformity	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
General disorders Non-cardiac Chest Pain	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Other - Erythema (left tibia)	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Hyperkeratosis	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Metabolism and nutrition disorders Other - Low Iron	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Other - Tachypnea	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Other - unspecified rash	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders other- Emphysema	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Injury, poisoning and procedural complications Other - hip pain	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Vascular disorders Other - Pulmonary embolism	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Musculoskeletal and connective tissue disorders Pain in Extremity	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Nervous system disorders Paresthesia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Eye disorders Periorbital Edema	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Platelet count decreased	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Pleural Effusion	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Nervous system disorders Presyncope	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Proteinuria	60.0% 6/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Rash maculo-papular	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Rectal Hemorrhage	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Renal and urinary disorders, other- Azotemia	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Renal Calculi	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Renal Colic	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Reproductive system and breast disorders Reproductive System and Breast Disorders, other- Primary ovarian insufficiency	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Eye disorders Retinal Detachment	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Cardiac disorders Sinus Tachycardia	20.0% 2/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Skin and subcutaneous tissue disorders, other- Grey hair	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Skin and subcutaneous tissue disorders Skin infection	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Neoplasms benign, malignant and unspecified (incl cysts and polyps) Skin Papilloma	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Thyroid Stimulating Hormone Increased	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Nervous system disorders Tremor	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Infections and infestations Upper Respiratory Infection	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Urinary Frequency	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Urinary incontinence	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Infections and infestations Urinary tract infection	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Renal and urinary disorders Urinary Urgency	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Gastrointestinal disorders Vomiting	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Eye disorders Watering Eyes	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Weight Gain	30.0% 3/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations Weight Loss	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Respiratory, thoracic and mediastinal disorders Wheezing	10.0% 1/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.
Investigations White Blood Cell Decreased	40.0% 4/10 • Adverse event data was collected at Day 2, 15, Months 1, 2, 3, long term, or subject death/lost to follow up, up to 17.8 months (for the longest follow up). Length of follow up for each subject is as follows: #1: 2.3 months, #2: 16.5 months, #3: 17.8 months, #4: 9.3 months, #5: 3 months, #6: 4.5 months, #7: 8.5 months, #8: 16 months, #9: 12 months, #10: 17.8 months. All AEs were collected and classified per CTCAE version 5.0. However, only those AEs and SAEs that were attributed by the investigators to be possibly, probably, or definitely related to FLASH radiotherapy were used for the assessment of toxicity of the FLASH treatment. There were no SAEs attributed to FLASH treatment, and the 7 AEs attributed to FLASH treatment were listed in the table as "Treatment Related". The remaining AEs in the table were unrelated to FLASH.

Additional Information

Senior Manager, Clinical Trials

Varian, a Siemens Healthineers Company

Phone: 437-991-3496

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee
Publication restrictions are in place