Loading
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.
These are the numbers GRAIL's US application rests on. Six in ten positive results were cancer and the predicted organ was usually right, but six in ten cancers diagnosed in the year were not flagged, and the study had no control group, so it cannot say whether testing changes outcomes.
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.
Set beside the result (35 cancers among 92 positives, positive predictive value 38%), it shows the test found fewer cancers than its makers had modelled.
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, NHS-Galleri, Positive predictive value (PPV).
Shares PATHFINDER 2, NHS-Galleri, Positive predictive value (PPV), Stage shift.
Shares PATHFINDER 2, NHS-Galleri, Positive predictive value (PPV), Stage shift.
Shares PATHFINDER 2, NHS-Galleri, Stage shift, Galleri.
Shares Performance of a multi-cancer early detection test in the randomized controlled NHS-Galleri trial, NHS-Galleri, Stage shift, Galleri.
Shares PATHFINDER (first prospective study of the Galleri test), The PATHFINDER Study: Assessment of the Implementation of an Investigational Multi-Cancer Early Detection Test into Clinical Practice, Performance and safety of a multi-cancer early detection test: the PATHFINDER 2 study, PATHFINDER 2.
Shares Stage shift, Overdiagnosis and false alarms, DNA methylation profiling, Multi-cancer early detection (MCED).
Shares PATHFINDER 2, NHS-Galleri, DNA methylation profiling, Multi-cancer early detection (MCED).
Every source this page cites, grouped by who published it. Grouping is read from the web address, not assigned by hand.
A source that has moved or gone is reported by the weekly link check. /audit/