New Blood Tests Promise Earlier Cancer Detection Before Tumors Form

Scientists are developing blood tests that can detect cancer long before symptoms appear, marking a shift from treating tumors to intercepting the disease decades before it develops. The approach targets biological processes and molecular warning signs that emerge years before cancer becomes obvious.

Scientists have designed a powerful light based sensor capable of detecting extremely small amounts of cancer biomarkers in blood. The innovation could eventually allow doctors to identify early warning signs of cancer and other diseases through a routine blood draw. The sensor combines nanostructures made of DNA with quantum dots and CRISPR gene editing technology to detect faint biomarker signals using a light-based approach known as second harmonic generation (SHG), according to research team leader Han Zhang from Shenzhen University in China.

In Optica, Optica Publishing Group's journal for high-impact research, the team reported that the device detected lung cancer biomarkers in patient samples at sub-attomolar levels. Even when only a few molecules were present, the system produced a clear and measurable signal. Because the platform is programmable, it could potentially be adapted to identify viruses, bacteria, environmental toxins, or biomarkers linked to conditions such as Alzheimer's disease.

The method holds promise for enabling simple blood screenings for lung cancer before a tumor might be visible on a CT scan. It could also help advance personalized treatment options by allowing doctors to monitor a patient's biomarker levels daily or weekly to assess drug efficacy, rather than waiting months for imaging results.

Most current biomarker tests require chemical amplification to increase tiny molecular signals, which adds time, complexity, and expense. The researchers aimed to create a direct detection strategy that eliminates those additional steps. The system relies on SHG, a nonlinear optical phenomenon in which incoming light is converted into light with half the wavelength. In this design, SHG takes place on the surface of a two dimensional semiconductor called molybdenum disulfide (MoS₂).

To precisely position the sensing components, the team built DNA tetrahedrons, which are small pyramid shaped nanostructures formed entirely from DNA. These structures hold quantum dots at carefully controlled distances from the MoS₂ surface. The quantum dots intensify the local optical field and boost the SHG signal. CRISPR-Cas gene editing technology was then incorporated to recognize specific biomarkers. When the Cas12a protein detects its target, it cuts the DNA strands that anchor the quantum dots. This action triggers a measurable drop in the SHG signal. Because SHG produces very little background noise, the system can detect extremely low biomarker concentrations with high sensitivity.

To evaluate real world performance, the researchers focused on miR-21, a microRNA biomarker associated with lung cancer. After confirming that the device could detect miR-21 in a controlled buffer solution, they tested it using human serum from lung cancer patients to simulate an actual blood test. The sensor worked exceptionally well, showing that integrating optics, nanomaterials and biology can be an effective strategy to optimize a device. The sensor was also highly specific, ignoring other similar RNA strands and detecting only the lung cancer target.

Scientists are also developing multi-cancer early detection tests (MCEDs), which search for tiny fragments of DNA in the blood. MCEDs work by looking for circulating tumour DNA, or ctDNA – DNA fragments that cancerous or precancerous cells release into the bloodstream. Even very early cancers shed this DNA, so the tests might detect disease long before it shows up on a scan.

MCEDs can boost survival rates through early detection, especially for colorectal cancer. When doctors diagnose colorectal cancer at stage one, 92% of patients survive five years. But when they catch it at stage four, only 18% survive that long. The tests aren't perfect, though. They miss some cancers entirely, and positive results still need follow-up tests to confirm. Even so, research suggests MCEDs could become crucial for catching cancers that usually go unnoticed until much later.

Researchers are hunting for subtle early warning signs that appear long before cancer becomes obvious. These include genetic mutations that quietly build up in cells, giving them advantages against immune defences. They're also looking at precancerous lesions like moles or polyps, and early visible changes in tissue.

Large genetic studies reveal that as people age, their bodies accumulate small groups of mutated cells called clones that grow silently. Scientists have studied this particularly well in blood. These clones can help predict who might develop blood cancers like leukaemia, and the genetics, inflammation and environmental factors strongly influence them. Crucially, doctors can measure and track these changes over time. This opens up possibilities for early intervention.

A 16-year study followed around 7,000 women and uncovered how these mutations work. Some mutations helped clones multiply faster, while others made them particularly sensitive to inflammation. When there was inflammation, these sensitive clones expanded. Breaking down these patterns helps researchers identify people with a higher chance of developing cancer later.

The research reveals something fundamental about cancer. It's not a sudden event that instantly produces a tumour. Instead, cancer develops through a slow, multi-step process with detectable warning signs along the way. These early signs could become powerful targets for stopping cancer before it starts.

Cancer researchers envision combining genetic mutations, environmental factors and MCED results to guide early cancer prevention. But cancer differs from heart disease in important ways. Cancer doesn't follow a predictable path, and some early lesions shrink or never progress. There's also the risk of over-diagnosis. Being told you're at higher risk when you feel perfectly healthy creates anxiety.

MCED tests bring their own ethical concerns. Accuracy isn't the only issue that matters. The tests sometimes flag cancer when none exists, leading to follow-up scans and biopsies that patients don't actually need. The anxiety from all of this carries a high cost, both for patients and the healthcare system. If these tests are expensive or only available privately, they could make health inequalities worse. This concern hits hardest in low-income countries.

In the US, the medicines regulator is investigating how MCED blood tests should work. They're examining how reliable the tests need to be and what follow-ups doctors should require to keep patients safe. The UK is following suit. The National Cancer Plan for England, published on February 4, 2026, commits to providing 9.5 million extra diagnostic tests through the NHS.

The next goal for the CRISPR sensor is to shrink the optical system. The researchers aim to develop a portable version that could be used at the bedside, in outpatient clinics, or in remote areas with limited medical resources.