# Performance and safety of a multi-cancer early detection test: the PATHFINDER 2 study

Source: https://onco.cc/key-papers/paper-pathfinder-2-nat-med-2026/  
OnCo record `paper-pathfinder-2-nat-med-2026` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

In 35,878 US adults aged 50 and over, the Galleri blood test was positive in a little over one in two hundred tested people who turned out to have cancer, six in ten positives were cancer, and it found about four in ten of the cancers diagnosed within a year.

## Summary

PATHFINDER 2 (NCT05155605) is GRAIL's prospective, interventional single-arm study of the Galleri test in people aged 50 or older without clinical suspicion of cancer, with co-primary endpoints of performance and safety after 12 months, analysed descriptively without hypothesis testing. Between December 2021 and July 2024, 35,878 participants were enrolled.

Among 32,007 performance-analysable participants the cancer detection rate was 0.54% (95% CI 0.47 to 0.63), positive predictive value 60.3% (54.5 to 65.8), negative predictive value 99.2% and specificity 99.64% (99.57 to 99.70). Episode sensitivity was 39.3% (34.9 to 44.0) for all cancers and 69.8% (62.8 to 76.0) for a prespecified 12-cancer subgroup; the number needed to screen to detect one cancer was 185, and cancer signal origin prediction accuracy was 91.3%. Among 35,335 safety-analysable participants, 213 (0.6%) had invasive procedures after a positive test, 90.5% of them non-surgical. The authors state that randomised trials and longer follow-up are needed to assess clinical utility.

## Fields

- Kind: Key paper
- Last checked: 2026-10-29
- Journal: Nature Medicine
- Year: 2026
- DOI: 10.1038/s41591-026-04618-w
- Authors: Nabavizadeh N, McDonnell C, Kurbegov D, et al.
- Findings: Cancer detection rate 0.54%; positive predictive value 60.3%; specificity 99.64%.; Episode sensitivity 39.3% for all cancers, 69.8% for the prespecified 12-cancer subgroup.; Number needed to screen to find one cancer: 185; cancer signal origin correct in 91.3%.; 213 of 35,335 (0.6%) had invasive procedures after a positive result.
- What it means: 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.
- Caveats: Single-arm and descriptive; no comparison group and no mortality or stage-shift endpoint.; The abstract gives no stage I sensitivity.; Sponsored by GRAIL.

## Sources

- Nature Medicine 2026: PATHFINDER 2: https://doi.org/10.1038/s41591-026-04618-w
- PubMed: https://pubmed.ncbi.nlm.nih.gov/42773207/
- ClinicalTrials.gov NCT05155605: https://clinicaltrials.gov/study/NCT05155605

## Connected records

- key papers: [PATHFINDER: the first prospective test of a multi-cancer blood test in people without symptoms](https://onco.cc/key-papers/paper-pathfinder-lancet-2023/)
- fronts: [Early Detection & Screening](https://onco.cc/fronts/early-detection/)
- technologies: [Cell-free DNA methylation tests](https://onco.cc/technologies/cfdna-methylation-testing/), [Liquid biopsy (ctDNA)](https://onco.cc/technologies/liquid-biopsy/), [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/), [Screening](https://onco.cc/terms/screening/)
- trials: [PATHFINDER 2](https://onco.cc/trials/pathfinder-2/)
- bottlenecks: [The hardest cancers are found late](https://onco.cc/bottlenecks/b-early-detection/)
- journals: [Nature Medicine](https://onco.cc/journals/nature-medicine/)

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