Multi-Cancer Early Detection: What the Galleri Trial Means for the Future

A large-scale trial of the Galleri multi-cancer early detection (MCED) test failed its primary goal of reducing late-stage cancer diagnoses, according to data presented at the American Society of Clinical Oncology (ASCO) meeting. The study, conducted in collaboration with the U.K.’s National Health Service (NHS), monitored 142,000 healthy participants aged 50 to 77 over three years.

Why did the Galleri cancer test trial fail?

The trial aimed to reduce the number of stage III and IV cancer cases by identifying the disease in stages I and II. According to Ruth Etzioni, a biostatistician at Fred Hutchinson Cancer Center, the test was “unexpectedly bad” at picking up those early-stage cancers. Etzioni told Live Science that the test appeared too conservative, applying a high threshold before registering a positive result.

Trial design also played a role. Etzioni noted that Galleri caught an unexpected number of advanced cancer cases during the first round of testing among volunteers who hadn’t been treated for cancer in three years. While excluding these initial cases might have improved performance, Etzioni believes the overall results would not have changed significantly.

Did You Know? The Galleri trial was the largest of its kind to date, recruiting 142,000 healthy volunteers and screening for markers linked to 12 different types of cancer.

How do multi-cancer early detection (MCED) tests work?

MCED tests use a single blood sample to screen for multiple cancers simultaneously. They detect cellular markers and disease-linked changes in DNA floating in the bloodstream. This approach targets cancers that currently lack established screening programs, such as pancreatic cancer, unlike colorectal cancer which is typically screened via colonoscopies.

However, the technology isn’t a universal solution. Jessica Lloyd, a strategic evidence manager at Cancer Research U.K., stated that while early detection drastically improves five-year survival rates for lung or colorectal cancers, it makes little difference for other types, such as melanoma.

What are the risks of early cancer detection?

The U.K. National Screening Committee (UK NSC) released a statement in May addressing “surrogate endpoints,” such as the cancer stages used in the Galleri trial. The committee warned that MCED tests may be biased toward detecting aggressive cancers rather than slow-growing ones.

GRAIL's NHS-Galleri Trial Results From ASCO 2026

This distinction is critical because patients with aggressive cancers may still die at similar rates even if detected early. Consequently, the UK NSC stated that further evaluation is likely required before any MCED test is adopted for widespread clinical practice within the NHS.

Expert Insight: Samantha Harrison, head of strategic evidence at Cancer Research U.K., described the failure to reach the trial’s main target as “disappointing.” She noted that the full value of the trial remains unclear until the massive dataset is detailed in a peer-reviewed publication.

What happens next for cancer screening technology?

Galleri is now focusing on the Real-world Evidence to Advance Multi-Cancer Early Detection Health Equity (REACH) study. This U.S.-based trial has enrolled 50,000 patients and measures the test’s ability to reduce stage IV diagnoses, a secondary endpoint where the NHS trial showed some success.

Other applications for the technology may include testing high-risk populations or patients with non-specific symptoms. Jessica Lloyd noted that another NHS trial, called SYMPLIFY, suggested the test was accurate when used specifically in symptomatic patient groups.

Ruth Etzioni believes MCEDs will eventually be used routinely, though she suggested the technology may not be “ready for prime time” yet. She noted that as newer tests develop and marker panels improve, performance could enhance.

Frequently Asked Questions

What was the primary endpoint of the Galleri trial?

The primary goal was to determine if the test could reduce the number of late-stage (stage III and IV) cancer cases identified among participants.

How many people participated in the NHS Galleri study?

The trial recruited 142,000 healthy people between the ages of 50 and 77.

Does early detection always improve patient survival?

No. According to Jessica Lloyd of Cancer Research U.K., early detection significantly helps survival for lung and colorectal cancers, but has little impact on overall survival rates for cancers like melanoma.

Do you believe blood-based screenings will eventually replace traditional cancer screenings?