Multi-cancer blood test did not lower late-stage cancers in its first large trial

A blood test designed to catch many cancers early did not reduce the rate of late-stage cancers when it was added to usual care, in the first large randomised trial to test whether such tests actually help [s1]. Across three annual screening rounds in England, the incidence-rate ratio for a stage III or IV cancer among screened participants versus a control group was 1.03, with a 95% confidence interval from 0.92 to 1.14 and a p-value of 0.63 — no difference [s1].

That primary result is the one that matters most, because it tests the core promise of the technology directly.

What the test is meant to do

Multi-cancer early-detection tests, or MCED tests, look for fragments of cancer-related DNA circulating in a tube of blood, and can flag a signal pointing to one of many cancer types at once [s1]. The test in this trial is made by Grail and marketed as Galleri. The logic behind it is a stage shift: if a test finds cancers earlier than they would otherwise present, more should be caught at stage I or II and fewer at the advanced stages III and IV, where treatment is harder and survival worse. Whether that shift happens in practice — rather than merely finding cancers that would have surfaced anyway, or flagging signals that lead nowhere — is exactly what a randomised trial is needed to settle.

The NHS-Galleri trial, run with NHS England and funded by Grail, was built to answer it [s1][s2]. It was registered as NCT05611632 [s2].

How the trial was run

Participants aged 50 to 77 years gave blood at up to three annual visits [s1]. After the first sample, they were randomly assigned in equal numbers to an intervention group, whose blood was tested, or a control group, whose blood was stored and not tested; participants and trial staff were initially unaware of the assignments [s1]. In all, 71,122 people were assigned to the intervention group and 71,128 to the control group [s1].

The primary endpoint was the rate of stage III or IV cancer across 12 prespecified cancer types, measured after three screening rounds and at least 12 months of further follow-up [s1]. A key secondary endpoint was the rate of stage IV cancer alone [s1].

What it found

The primary endpoint did not move. The incidence-rate ratio for stage III or IV cancer was 1.03 (95% CI, 0.92 to 1.14; P=0.63) — the confidence interval sits squarely across 1.0, meaning the screened and unscreened groups had statistically indistinguishable rates of advanced cancer [s1].

The stage IV secondary endpoint pointed in a more favourable direction: an incidence-rate ratio of 0.86, with a 95% confidence interval from 0.74 to 1.00 [s1]. That is a possible reduction in the most advanced cancers, but the interval reaches right up to 1.0, so it is a signal to follow rather than a proven benefit — and because the primary endpoint was not met, a secondary finding cannot carry the conclusion on its own. Fewer than 1% of participants had a trial-related adverse event, and none were serious [s1].

What it does and does not establish

The honest reading is narrow. After three rounds of screening, adding an MCED test to usual care did not lower the rate of stage III or IV cancers across the 12 cancer types studied [s1]. The stage IV difference keeps the door open, and the investigators say further follow-up is warranted to see how both findings evolve, since a test given repeatedly may separate from usual care only over more years [s1].

This is the trial the field had been waiting for. As an explainer on multi-cancer blood tests on this site set out, these tests can flag a cancer signal and often guess its origin, but no trial had yet shown they help people — and a test's ability to detect cancer is not the same as a demonstrated benefit from using it. NHS-Galleri now supplies the first randomised answer on late-stage disease, and on its primary measure that answer is null.

The result is a company-funded trial reporting a negative primary endpoint, which is worth stating plainly: the finding runs against the commercial interest behind the test, and that makes the null harder to dismiss [s1]. It also sits within a wider, unresolved argument about whether earlier detection reliably translates into longer or better lives, a question that has dogged screening from mammography to colorectal testing.

What to watch

Longer follow-up from NHS-Galleri will show whether the stage IV signal firms up or fades, and whether any stage shift eventually produces a mortality benefit — the outcome that ultimately decides whether population screening with these tests is worth it. Until then, the trial is a caution against rolling out multi-cancer blood tests on the strength of their detection performance alone.

This article describes trial results. It is not medical advice, and nothing here should be used to decide whether to seek or forgo cancer screening.

Sources

• Effect of Screening with Multicancer Early-Detection Test on Late-Stage Cancer Diagnosis, New England Journal of Medicine, 22 September 2026
• The NHS-Galleri Trial (NCT05611632), ClinicalTrials.gov