Blood Test May Help Detect Some Cancers Earlier, Study Finds

A blood test designed to detect dozens of cancers before symptoms appear may help identify some cancers earlier and reduce the number diagnosed at the most advanced stage, according to results from a large randomized clinical trial presented at the 2026 American Society of Clinical Oncology Annual Meeting. 

Researchers reported that participants who received annual screening with the Galleri multi-cancer early detection test were less likely to be diagnosed with stage 4 cancer and had fewer cancers detected after symptoms developed compared with people who received standard cancer screening alone. However, the study did not meet its primary endpoint of significantly reducing the number of late-stage cancers overall. 

🚨New results presented at #ASCO26 from the NHS-Galleri trial suggest multicancer early detection blood testing increased screen-detected cancers while reducing stage IV diagnoses and emergency cancer presentations.

Moffitt’s Marilyn Bui, MD (@DrBuiPathology), discusses the… pic.twitter.com/mh4ikRhBZu

— Moffitt Cancer Center (@MoffittNews) May 30, 2026

The findings come from the NHS-Galleri trial, the first randomized controlled study to report results for a multi-cancer early detection test. Researchers say the results provide an important early look at how blood-based cancer screening could potentially complement existing screening programs in the future. 

Testing For Cancers Without Screening Options 

Unlike traditional screening tests that target a single cancer type, the Galleri test analyzes fragments of DNA circulating in the bloodstream and searches for patterns associated with cancer. Previous studies have shown the test can detect signals from more than 50 types of cancer, including many that currently have no recommended screening methods. 

The NHS-Galleri trial enrolled more than 140,000 people between ages 50 and 77 in the United Kingdom who had no symptoms of cancer. Participants continued to receive standard cancer screenings and annual blood draws over a three-year period. 

Half of the participants were randomly assigned to have their blood samples analyzed using the Galleri test, while the other half served as a control group and did not receive the blood test. Individuals with positive results underwent additional diagnostic testing to determine whether cancer was present. 

Lead study author Charles Swanton, MD, PhD, from the University College London Cancer Institute in London, says the trial demonstrates that large-scale implementation of multi-cancer screening is possible within a national health care system. 

 “The trial demonstrates that annual multi-cancer early detection testing is feasible at scale within a national health system and can increase the number of cancers detected through screening, including many for which no organized program currently exists,” Swanton said. 

Signs of a Stage Shift 

Researchers diagnosed more than 7,000 cancers during the study period, including 3,637 in the Galleri group and 3,400 in the control group. Screening identified four times as many cancers in participants who received the blood test compared with those who received standard screening alone. 

Although the study did not achieve its primary goal of significantly reducing stage 3 and 4 diagnoses among a group of 12 prespecified cancers, researchers observed encouraging shifts in when cancers were detected. 

Theresa Boyle, MD, PhD

Among those cancers, participants in the Galleri group experienced 14% fewer stage 4 diagnoses and 19% more diagnoses at stages 1, 2 or 3 compared with the control group. Researchers also found that participants receiving the blood test had 21% fewer cancers detected because of symptoms and 20% fewer cancers identified through emergency presentations, situations that are often associated with more advanced disease. 

Theresa Boyle, MD, PhD, a pathologist at Moffitt Cancer Center, says these findings are potentially important because outcomes are generally much better when cancer is found before it has spread. 

“Detecting cancer at an earlier stage exponentially increases the chances that the cancer can be entirely eliminated by surgery, radiotherapy or medicines,” Boyle said. “With stage 4 cancer, the cancer has usually spread and it is much more challenging to eliminate every cancer cell, with much higher odds of cancer progression than treated early-stage cancer.”  

Important Questions Remain 

While the results suggest the test may influence when cancer is detected, researchers caution that it remains unclear whether earlier detection through multi-cancer early detection testing ultimately improves survival. 

The study was not designed to determine whether finding cancers sooner leads to patients living longer. Investigators also noted that some cancers detected by screening may never have become symptomatic during a person's lifetime, raising important questions about overdiagnosis and the balance between benefits and potential harms. 

The Galleri test demonstrated a specificity of 99.55%, meaning false-positive results were relatively uncommon. When the test detected cancer, it accurately predicted the site of origin in most cases, correctly identifying the cancer location in 87% of patients when one site was reported and more than 92% when the top two likely sites were considered. 

Researchers reported no serious adverse events related to testing, although some participants experienced temporary anxiety following positive results and underwent additional diagnostic evaluations. 

Boyle said multi-cancer early detection tests could eventually fill an important gap by helping detect cancers that currently lack routine screening options. 

“Multi-cancer early detection tests can be life-saving with earlier medical intervention,” Boyle said. “They can detect cancers earlier that are usually not detected until late stage, some of which don’t currently have routine screening tests available, such as pancreatic and ovarian cancer.” 

At the same time, she emphasized that important questions remain before widespread adoption. 

“The best screening test may be the one that people actually use. Blood testing is convenient and could be checked routinely in conjunction with cholesterol screening,” Boyle said. “However, the costs and risks of both false-negative and false-positive results need to be considered relative to other screening assays before widespread adoption.”  

Looking Toward the Future 

Researchers will continue following participants to determine whether the observed reduction in stage 4 diagnoses grows over time and whether earlier detection ultimately translates into longer survival. Additional studies will also evaluate the costs, benefits and practical implications of incorporating multi-cancer early detection testing into routine cancer screening programs. 

Christine Walko, PharmD

Christine Walko, PharmD, chair of the Individualized Cancer Management Department at Moffitt, says the trial's findings should be viewed in the context of how new screening programs are expected to perform over time. 

“As this is a new potential screening paradigm, as Dr. Swanton explained, if a screening modality works, we would initially expect to see an increase in advanced or previously undiagnosed cancers present at the time of enrollment,” Walko said. “This would then decrease over time, which is what was observed in the trial, though with wide confidence intervals. Longer follow-up is now planned, which will provide data regarding whether decreases in advanced cancers continued to occur over time.” 

Walko says the Galleri study represents an important step in evaluating whether circulating cell-free DNA can be used to screen for cancers that currently lack recommended screening tests. 

“The Galleri trial is an exciting new application of utilization of cell-free DNA to potentially address the need for a successful screening tool for cancers without recommended screening tests,” she said. “A planned nested mortality analysis is being conducted to help elucidate which patients may benefit the most from this type of screening, potentially considering risk factors and type of cancer.” 

For now, investigators say the trial represents an important milestone for a technology that could eventually expand cancer screening beyond the handful of cancers currently included in public health guidelines. 

As researchers continue to refine multi-cancer detection approaches, studies like NHS-Galleri are helping answer one of oncology's most important questions: whether finding more cancers earlier can meaningfully change outcomes for patients.