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In 6,621 adults over 50, the Galleri test flagged a cancer signal in 1.4%, of whom 38% turned out to have cancer; diagnostic work-up took about two months for true positives and over five months for false positives.
PATHFINDER was a single-arm prospective study in which 6,621 adults aged 50 or over at seven US health systems had the Galleri methylation-based multi-cancer early detection (MCED) test in addition to standard screening. A cancer signal triggered clinician-directed diagnostic evaluation guided by the predicted cancer signal origin.
A signal was detected in 92 participants (1.4%); 35 had cancer confirmed, giving a positive predictive value of 38%. Specificity was 99.1% and the cancer signal origin prediction was correct in the large majority of true positives. Median time to diagnostic resolution was 79 days: 57 days for true positives and 162 days for false positives. Almost half of the cancers detected were early stage, and several were in organs without standard screening.
The study established feasibility and the diagnostic pathway and set the stage for the randomised NHS-Galleri trial and the larger PATHFINDER 2.
A multi-cancer blood test can be run in ordinary clinics, and most positive results can be resolved with imaging. But six in ten positives are false alarms that take months to resolve, and the test misses most cancers. Whether it reduces late-stage cancer or deaths is unknown; that requires randomised trials.
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.
A blood test can find early, treatable cancers in people who feel well, including cancers for which no screening exists. It is not a replacement for mammography or colonoscopy but a possible addition. Larger randomised trials are needed to show benefit outweighs harm.
Shares PATHFINDER 2, Performance of a multi-cancer early detection test in the randomized controlled NHS-Galleri trial, Galleri, NHS-Galleri.
Shares PATHFINDER 2, Galleri, NHS-Galleri, Positive predictive value (PPV).
Shares PATHFINDER 2, Galleri, NHS-Galleri, Positive predictive value (PPV).
Shares PATHFINDER 2, Performance of a multi-cancer early detection test in the randomized controlled NHS-Galleri trial, Galleri, NHS-Galleri.
Shares PATHFINDER 2, Galleri, NHS-Galleri, Stage shift.
Shares PATHFINDER 2, Performance of a multi-cancer early detection test in the randomized controlled NHS-Galleri trial, Galleri, NHS-Galleri.
Shares Stage shift, Multi-cancer early detection (MCED), Overdiagnosis and false alarms, DNA methylation profiling.
Shares PATHFINDER 2, NHS-Galleri, Multi-cancer early detection (MCED), DNA methylation profiling.