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The largest cancer screening trial ever run, testing whether a multi-cancer blood test reduces late-stage diagnoses; it reports that it did not, and its test-performance paper appeared in Nature Medicine on 22 September 2026.
NHS-Galleri (ISRCTN91431511; ClinicalTrials.gov NCT05611632) randomised 142,250 people aged 50 to 77 in England 1:1 to GRAIL's Galleri multi-cancer early detection (MCED) test added to usual NHS care, or to control, with three annual screening rounds; positive results were referred to NHS standard-of-care diagnostic pathways informed by the predicted cancer signal origin. The primary endpoint was a reduction in the incidence of stage III/IV cancer diagnoses in the intervention arm versus control, tested first in 12 prespecified cancer types (lung, head and neck, colorectal, pancreas, myeloma or plasma cell neoplasm, liver or bile duct, stomach, oesophagus, anus, lymphoma, ovary and bladder).
The test-performance paper in Nature Medicine (22 September 2026) states that the primary endpoint was not met and was reported elsewhere; no peer-reviewed primary-endpoint paper was indexed on Europe PMC by 23 September 2026, so the primary result rests on that statement and on GRAIL's 30 May 2026 release. The paper's own figures, for the intervention arm: positive results in 1.03, 0.80 and 0.90 percent of participants in rounds 1 to 3; 937 MCED-detected primary cancers in aggregate; cancer detection rates 0.60, 0.40 and 0.41 percent; positive predictive values 58.0, 50.4 and 45.8 percent; negative predictive values 98.98, 98.90 and 98.86 percent; specificity 99.50 to 99.60 percent; episode sensitivity 26.7 to 37.2 percent for all cancers and 47.6 to 63.4 percent for the 12 prespecified types.
The registry lists the trial as active, not recruiting, with 142,318 participants, primary completion on 12 June 2026 and study completion in January 2031 for longer follow-up including cancer-specific mortality. The data feed GRAIL's FDA premarket approval application and the advisory committee of 23 September 2026.
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.
142,250 randomised.
Not met, per the Nature Medicine test-performance paper (22 September 2026), which states the primary endpoint was not met and reported elsewhere; no peer-reviewed primary-endpoint paper was on Europe PMC by 23 September 2026, so no figures are recorded here.
Source722, 518 and 561 positive results among evaluable intervention-arm participants
Source937 participants had MCED-detected primary cancers across the three rounds
Source419/722, 261/518 and 257/561
Source68,895/69,603, 63,278/63,980 and 61,058/61,762
SourceThe abstract gives the range across rounds 1 to 3, not per-round values
SourceRange across rounds 1 to 3 as given in the abstract
SourceRange across rounds 1 to 3 as given in the abstract
SourceRelative reduction versus control in the 12 prespecified cancers, from GRAIL's release of 30 May 2026; not in the Nature Medicine paper
SourceFrom GRAIL's release of 30 May 2026; not in the Nature Medicine paper
Source| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Stage III to IV incidence, 12 prespecified cancers (primary)primary | Galleri + usual NHS care | - | Not met, per the Nature Medicine test-performance paper (22 September 2026), which states the primary endpoint was not met and reported elsewhere; no peer-reviewed primary-endpoint paper was on Europe PMC by 23 September 2026, so no figures are recorded here. | - | - | link |
| Usual NHS care | - | - | ||||
| Positive test results by screening round | Round 1 | 70,325 | 1.03% | - | - | link |
| Round 2 | 64,498 | 0.8% | ||||
| Round 3 | 62,323 | 0.9% | ||||
| Cancer detection rate by screening round | Round 1 | 70,325 | 0.6% | - | - | link |
| Round 2 | 64,498 | 0.4% | ||||
| Round 3 | 62,323 | 0.41% | ||||
| Positive predictive value by screening round | Round 1 | 722 | 58% | - | - | link |
| Round 2 | 518 | 50.4% | ||||
| Round 3 | 561 | 45.8% | ||||
| Negative predictive value by screening round | Round 1 | 69,603 | 98.98% | - | - | link |
| Round 2 | 63,980 | 98.9% | ||||
| Round 3 | 61,762 | 98.86% | ||||
| Specificity, range across rounds | Lowest round | - | 99.5% | - | - | link |
| Highest round | - | 99.6% | ||||
| Episode sensitivity, all cancers, range across rounds | Lowest round | - | 26.7% | - | - | link |
| Highest round | - | 37.2% | ||||
| Episode sensitivity, 12 prespecified cancer types, range across rounds | Lowest round | - | 47.6% | - | - | link |
| Highest round | - | 63.4% | ||||
| Cancer signal origin accuracy, range across rounds | Lowest round | - | 91.1% | - | - | link |
| Highest round | - | 93.6% | ||||
| 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 |
For someone offered the test, these are the numbers that describe what a result means in an NHS population: about 1 in 100 tests came back positive each year, between 46 and 58 in 100 positives were cancer, and a negative result left about 1 in 100 with an undetected cancer within the year. The test found between a quarter and a third of all cancers diagnosed in a screening round, and about half to two thirds of the 12 cancer types it was designed to find. Whether finding them this way reduces late-stage diagnoses is the primary question, and this paper says only that the answer was no; the primary-endpoint paper had not appeared on Europe PMC by 23 September 2026.
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, Eric A. Klein, Pre-agreed update rules so an MCED test is not obsolete when its trial reads out, Vanguard Study (NCI Cancer Screening Research Network).
Shares Cell-free DNA methylation tests, Galleri, Positive predictive value (PPV), Stage shift.
Shares Cell-free DNA methylation tests, GRAIL, Galleri, Multi-cancer early detection (MCED).
Shares A whole-population cancer interception programme: risk-stratify every adult, detect and intercept early, Galleri, Multi-cancer early detection (MCED), The hardest cancers are found late.
Shares Vanguard Study (NCI Cancer Screening Research Network), NHS-Galleri: design of the largest randomised trial of a multi-cancer blood test, Stage shift, Multi-cancer early detection (MCED).
Shares GRAIL, Galleri, Positive predictive value (PPV), Multi-cancer early detection (MCED).
Shares Anal cancer (squamous cell carcinoma), Oesophageal cancer, Biliary tract cancer (cholangiocarcinoma), Hepatocellular carcinoma.
Shares Galleri, Positive predictive value (PPV), Screening, Multi-cancer early detection (MCED).