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In the NHS-Galleri trial about one person in a hundred had a positive blood test in each of three yearly rounds, roughly half of those positives were cancer, and the test missed most cancers diagnosed during the trial. The paper says the main endpoint, fewer late-stage diagnoses, was not met and is reported elsewhere.
Prespecified secondary test-performance analysis of NHS-Galleri, the randomised controlled trial of GRAIL's Galleri multi-cancer early detection (MCED) test added to usual NHS care. Participants aged 50 to 77 (N = 142,250) were randomised 1:1 to the MCED test or control; intervention-arm participants with a positive result were referred to NHS standard-of-care diagnostic pathways, with referrals informed by the predicted cancer signal origin. The analyses were descriptive, with no hypothesis testing. The abstract states that the primary endpoint, a reduction in the incidence of stage III/IV cancer diagnoses in the intervention arm versus the control arm, was not met and was reported elsewhere.
Positive results were returned for 722 of 70,325 (1.03 percent), 518 of 64,498 (0.80 percent) and 561 of 62,323 (0.90 percent) participants in rounds 1 to 3. In aggregate 937 participants had MCED-detected primary cancers. By-round cancer detection rates were 0.60, 0.40 and 0.41 percent; positive predictive values 58.0 percent (419/722), 50.4 percent (261/518) and 45.8 percent (257/561); negative predictive values 98.98 percent (68,895/69,603), 98.90 percent (63,278/63,980) and 98.86 percent (61,058/61,762). Across rounds, specificity ranged from 99.50 to 99.60 percent, episode sensitivity from 26.7 to 37.2 percent for all cancers and from 47.6 to 63.4 percent for 12 prespecified cancer types, and cancer signal origin accuracy from 91.1 to 93.6 percent. The 12 prespecified types are named on the ClinicalTrials.gov record (NCT05611632): lung, head and neck, colorectal, pancreas, myeloma or plasma cell neoplasm, liver or bile duct, stomach, oesophagus, anus, lymphoma, ovary and bladder.
For someone offered the test, these are the numbers that describe what a result means in an NHS population: about 1 in 100 tests came back positive each year, between 46 and 58 in 100 positives were cancer, and a negative result left about 1 in 100 with an undetected cancer within the year. The test found between a quarter and a third of all cancers diagnosed in a screening round, and about half to two thirds of the 12 cancer types it was designed to find. Whether finding them this way reduces late-stage diagnoses is the primary question, and this paper says only that the answer was no; the primary-endpoint paper had not appeared on Europe PMC by 23 September 2026.
Shares Cell-free DNA methylation tests, GRAIL, NHS-Galleri: design of the largest randomised trial of a multi-cancer blood test, PATHFINDER: the first prospective test of a multi-cancer blood test in people without symptoms.
Shares Cell-free DNA methylation tests, Galleri, Positive predictive value (PPV), Stage shift.
Shares Cell-free DNA methylation tests, GRAIL, Galleri, Multi-cancer early detection (MCED).
Shares Galleri, NHS-Galleri, Positive predictive value (PPV), Stage shift.
Shares NHS-Galleri: design of the largest randomised trial of a multi-cancer blood test, Galleri, NHS-Galleri, Stage shift.
Shares Galleri, NHS-Galleri, Positive predictive value (PPV), Stage shift.
Shares NHS-Galleri: design of the largest randomised trial of a multi-cancer blood test, Galleri, NHS-Galleri, Positive predictive value (PPV).
Shares PATHFINDER: the first prospective test of a multi-cancer blood test in people without symptoms, Galleri, NHS-Galleri, Multi-cancer early detection (MCED).