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PATHFINDER 2 is the US real-world study of the Galleri test that forms the core of its FDA submission.
PATHFINDER 2, trial NCT05155605 sponsored by GRAIL and reported in 2025, is the US real-world study of the Galleri multi-cancer blood test that forms the core of its FDA submission. It enrolled about 35,000 adults aged fifty or over who received Galleri alongside standard screening in a single-arm design, with 25,490 participants and one-year follow-up in the premarket approval application; a cancer signal was detected in about one percent, the positive predictive value was around sixty percent with very high specificity, and GRAIL reported at ESMO 2025 that adding the test found several times more cancers than standard screening alone. It improves on PATHFINDER 1, but the randomised NHS-Galleri trial did not meet its stage-shift endpoint, so whether detection translates into benefit is the open question.
Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.
35,883 enrolled.
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Cancer signal detected | Galleri, all participants | 25,578 | 0.93% | - | - | link |
| Positive predictive value | Galleri | - | 61.6% | - | - | link |
| Specificity | Galleri | - | 99.6% | - | - | link |
The full inclusion and exclusion criteria are on the registry record. Read 2026-10-07. Recruiting overall does not mean a particular site is open; ask the study team.
ClinicalTrials.gov data courtesy of the US National Library of Medicine.
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.
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.
NHS-Galleri is the trial that will decide whether a blood test for many cancers at once should be offered by a health system. Its endpoint is a reduction in late-stage cancer rather than deaths, so even a positive result leaves the mortality question to be settled by longer follow-up.
Shares Deborah Schrag, Pre-agreed update rules so an MCED test is not obsolete when its trial reads out, Eric A. Klein, Let MCED trials read out on late-stage incidence, with mortality follow-up mandated.
Shares PATHFINDER (first prospective study of the Galleri test), PATHFINDER: the first prospective test of a multi-cancer blood test in people without symptoms, GRAIL, Positive predictive value (PPV).
Shares 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, Cell-free DNA methylation tests, GRAIL.
Shares Eric A. Klein, Cell-free DNA methylation tests, GRAIL, Galleri.
Shares Cell-free DNA methylation tests, GRAIL, Positive predictive value (PPV), Galleri.
Shares Eric A. Klein, Cell-free DNA methylation tests, GRAIL, Galleri.
Shares NHS-Galleri: design of the largest randomised trial of a multi-cancer blood test, Cell-free DNA methylation tests, GRAIL, Galleri.
Shares GRAIL, Positive predictive value (PPV), Galleri, 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/