NHS-Galleri
The largest cancer screening trial ever run, testing whether a multi-cancer blood test reduces late-stage diagnoses.
Primary endpoint: reduction in stage III-IV cancer incidence. Interim 2024 results did not trigger early NHS rollout. Final results presented at ASCO 2026: the primary endpoint (stage III-IV reduction) was not met, while stage IV incidence fell by about 14%; the data feed the FDA PMA and the September 2026 advisory committee. See the ASCO 2026 digest for sources.
- Numbers are not recorded here for this endpoint. Galleri + standard screening: Not met: no statistically significant reduction within one year of the last screen; a fall in stage IV was offset by a rise in stage III.; Standard screening.
- 22 vs 26 out of 100 reached this endpoint with Round 2 compared with Round 3; 4 fewer per 100.
- On this measure the first group did worse, not better.
- 25 out of 100 people reached this endpoint with Galleri + standard screening.
- There was no comparison group, so this number cannot tell you how much of the effect is due to the treatment.
- This endpoint is not one of the standard survival or response measures; read it alongside the trial's primary result.
- These results apply to the people the trial enrolled: 140,000 asymptomatic adults aged 50-77 randomised to annual Galleri testing or control for 3 years. People in a different situation may not see the same effect.
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.
142,000 participants enrolled.
Not met: no statistically significant reduction within one year of the last screen; a fall in stage IV was offset by a rise in stage III.
SourceRelative reduction versus control in the 12 prespecified cancers
Source| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Stage III–IV incidence, 12 prespecified cancers (primary)primary | Galleri + standard screening | — | Not met: no statistically significant reduction within one year of the last screen; a fall in stage IV was offset by a rise in stage III. | — | — | link |
| Standard screening | — | — | ||||
| Relative reduction in stage IV diagnoses, rounds 2 and 3 | Round 2 | — | 22% | — | — | link |
| Round 3 | — | 26% | ||||
| Relative reduction in diagnosis through emergency presentation | Galleri + standard screening | — | 25% | — | — | link |
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.