# PATHFINDER 2

Source: https://onco.cc/trials/pathfinder-2/  
OnCo record `pathfinder-2` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

PATHFINDER 2 is the US real-world study of the Galleri test that forms the core of its FDA submission.

## Summary

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.

## Fields

- Kind: Trial
- Status: active
- Last checked: 2026-09-04
- Registry id: NCT05155605
- Phase: observational
- Setting: ~35,000 adults ≥50 receiving Galleri alongside standard screening, single-arm
- Sponsor: GRAIL
- Enrolled: 35883
- Outcomes: Cancer signal detected: Galleri, all participants 0.93%; Positive predictive value: Galleri 61.6%; Specificity: Galleri 99.6%
- Replication: Improves on PATHFINDER 1 (PPV 43%) with the refined classifier; the randomised NHS-Galleri trial did not meet its stage-shift primary endpoint.

## Sources

- ClinicalTrials.gov NCT05155605: https://clinicaltrials.gov/study/NCT05155605

## Connected records

- technologies: [Cell-free DNA methylation tests](https://onco.cc/technologies/cfdna-methylation-testing/), [DNA methylation profiling](https://onco.cc/technologies/methylation-profiling/), [Multi-cancer early detection (MCED)](https://onco.cc/technologies/mced/)
- drugs: [Galleri](https://onco.cc/drugs/galleri/)
- companies: [GRAIL](https://onco.cc/companies/grail/)
- terms: [Positive predictive value (PPV)](https://onco.cc/terms/ppv/), [Real-world evidence](https://onco.cc/terms/real-world-evidence/), [Single-arm trial](https://onco.cc/terms/single-arm/)
- people: [Deborah Schrag](https://onco.cc/people/deb-schrag/), [Eric A. Klein](https://onco.cc/people/eric-klein/)
- roadmaps: [ctDNA tests roadmap: from a curiosity in plasma to blood tests that decide treatment](https://onco.cc/roadmaps/ctdna-tests/), [Early detection roadmap: organ screening → blood tests for many cancers](https://onco.cc/roadmaps/early-detection-roadmap/)
- bottlenecks: [The hardest cancers are found late](https://onco.cc/bottlenecks/b-early-detection/)
- ideas: [A whole-population cancer interception programme: risk-stratify every adult, detect and intercept early](https://onco.cc/ideas/idea-moon-population-interception/), [Let MCED trials read out on late-stage incidence, with mortality follow-up mandated](https://onco.cc/ideas/idea-prev-mced-stage-endpoint-surrogate/), [Pre-agreed update rules so an MCED test is not obsolete when its trial reads out](https://onco.cc/ideas/idea-prev-mced-change-control-plan/)
- key papers: [NHS-Galleri: design of the largest randomised trial of a multi-cancer blood test](https://onco.cc/key-papers/paper-nhs-galleri-design-cancers-2022/), [PATHFINDER: the first prospective test of a multi-cancer blood test in people without symptoms](https://onco.cc/key-papers/paper-pathfinder-lancet-2023/)
- trials: [Vanguard Study (NCI Cancer Screening Research Network)](https://onco.cc/trials/vanguard-study/)

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