Longevity clinic
Galleri (Grail Multi-Cancer Early Detection)
Last updated Sun May 17 2026 00:00:00 GMT+0000 (Coordinated Universal Time)
What it is
Galleri is a multi-cancer early-detection (MCED) blood test developed by Grail (now back under Illumina). It analyses circulating cell-free-DNA methylation patterns to screen for >50 cancer types, many of which lack any other routine screening test, and predicts the tissue of origin for positive signals.
Performance
- Specificity is ~99% (few false positives).
- Sensitivity varies by cancer type and stage; overall ~50–55% across all cancers and stages, higher for stage III/IV and certain cancers (head/neck, oesophageal, ovarian).
- Tissue-of-origin prediction ~88% accurate when correct.
What we don’t yet know
- Whether MCED screening reduces cancer mortality — the randomised UK NHS-Galleri trial (~140,000 enrollees) is expected to report later this decade.
- Optimal age and frequency of testing.
- Cost-effectiveness in different populations.
Trade-offs to discuss before testing
- Positive results lead to diagnostic workups that can be invasive and anxiety-provoking, including some that turn out negative.
- Negative results do not mean no cancer — sensitivity is far from 100% even at moderate stages.
- Out-of-pocket cost is significant.
- Doesn’t replace standard screening (colonoscopy, mammography, etc.).
Related entries
References
- Klein, E. A. et al. Clinical validation of a targeted methylation-based multi-cancer early detection test using an independent validation set (PATHFINDER). Ann. Oncol. 32, 1167–1177 (2021).