A major clinical trial evaluating a single blood test designed to detect multiple cancers at an early stage failed to meet its primary endpoint. However, results presented at the 2026 ASCO Annual Meeting showed reductions in Stage IV cancer diagnoses and increases in the detection of earlier-stage cancers.
Developing a single blood test capable of detecting multiple types of cancer before symptoms appear has become a major goal of cancer screening research.
U.S.-based biotechnology company GRAIL has been among the leading developers in the field with its Galleri multi-cancer early detection test.
The NHS-Galleri trial, conducted in partnership with England's National Health Service, enrolled more than 142,000 people aged 50 to 77 who had no symptoms suggesting cancer at enrollment. Participants were randomly assigned to receive annual Galleri testing in addition to standard NHS care or standard care alone.
Primary endpoint was not met
The primary objective of the trial was to determine whether adding Galleri to standard care could reduce the incidence of Stage III and IV cancers.
Results presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting showed that the trial did not demonstrate a statistically significant reduction in combined Stage III-IV cancers across three screening rounds in the prespecified group of 12 cancer types.
As a result, the trial did not meet its primary endpoint.
However, the study produced positive findings on several secondary outcomes.
Stage IV diagnoses declined
According to detailed results presented by GRAIL at ASCO, Galleri reduced Stage IV diagnoses of 12 prespecified cancer types by 22% during the second screening round and by 26% during the third screening round.
Adding Galleri to standard-of-care screening also increased the overall cancer detection rate approximately fourfold. The study also reported an increase in the detection of Stage I and II cancers.
The findings suggest that the test may have the potential to identify some cancers before they progress to advanced disease. However, failure to meet the primary endpoint means that the clinical benefit of population-wide screening with the test has not yet been definitively established.
Test is not a replacement for standard screening
Galleri analyzes biological signals in the blood associated with cancer and attempts to predict the tissue or organ where a cancer signal may have originated.
However, the test does not detect all cancers and is not intended to replace established screening methods such as mammography, colonoscopy or cervical cancer screening. GRAIL recommends that Galleri be used in addition to, rather than instead of, recommended cancer screening.
One of the major findings was the increase in cancer detection when Galleri was added to standard screening. Researchers still need longer-term data to determine whether earlier detection ultimately translates into better treatment outcomes and lower cancer mortality.
Further research is needed
The NHS-Galleri trial is one of the largest randomized controlled studies to evaluate a multi-cancer early detection test at population scale.
GRAIL has said that longer follow-up could provide additional information about the clinical impact of the test. The company is also continuing to evaluate Galleri through additional studies examining its safety, cancer detection performance and potential clinical use.
The key question for researchers is not simply whether a blood test can detect cancer earlier, but whether earlier detection ultimately improves treatment outcomes and reduces cancer deaths. Longer-term follow-up will therefore be critical in determining the role of multi-cancer early detection tests in routine population screening.
Kaynak: The Lancet
