NHS cancer blood test Galleri fails primary trial goal despite mixed results

A three-year trial of more than 142,000 NHS patients has ended without delivering what health officials had promised: a blood test that could catch cancer earlier and save lives. The Galleri test, which hunts for fragments of tumour DNA in the bloodstream, was supposed to reduce the number of cancers diagnosed at the most advanced stages—stage three and four—where treatment becomes harder and survival rates drop. The trial, which cost £150 million, split participants aged 50 to 77 into two groups: half received the annual blood test, while the other half followed standard NHS screening protocols. When the results were tallied, the test had failed to meet its primary objective.

Yet the picture was not entirely bleak. Stage four cancers—the most advanced form—fell by more than a fifth among those who received the Galleri test. This was a meaningful reduction, the kind of finding that might ordinarily be celebrated. But it came with a complication. The number of stage three cancers increased in the test group, offsetting much of the gain. Sir Harpal Kumar, chief scientific officer at Grail, the company that manufactures the test, acknowledged this tension. He suggested that some of the stage four cancers had simply been caught earlier, shifting to stage three rather than disappearing entirely. The net effect was that the trial had not achieved what it set out to do: reduce late-stage diagnoses overall.

The Galleri test itself is a sophisticated tool. It can detect more than 50 different types of cancer by identifying tumour DNA fragments in blood samples. The trial focused on 12 cancer types that together account for roughly two-thirds of cancer deaths in the UK. When the test was first being developed, the promise seemed immense. In 2021, Amanda Pritchard, who was then NHS chief executive, had called it a potential watershed moment, suggesting it could "mark the beginning of a revolution in cancer detection and treatment here and around the world." That language set high expectations.

The trial results were presented at the American Society of Clinical Oncology's annual conference in Chicago in May 2026. Julie Gralow, the organisation's chief medical officer, was direct in her assessment: the test "will not get approval in the NHS based on this data." That statement effectively closed the door on any near-term rollout of Galleri across the health service. The mixed results—some positive signals alongside a missed primary goal—were not enough to justify the kind of system-wide adoption that had been discussed.

Experts have raised deeper questions about what the trial actually proved. Professor Richard Houlston of The Institute of Cancer Research in London cautioned that researchers might be "moving the goal posts" by emphasizing positive findings when the main objective had not been met. He argued that the only truly reliable way to evaluate such a test would be a trial that tracked patients' survival rates over time. But he also acknowledged a cruel paradox: running such a trial to completion would take close to two decades. By the time researchers had their answer, the technology itself would likely be outdated, making the findings obsolete before they could be acted upon.

The NHS has not closed the door entirely. Professor Peter Johnson, the national clinical director for cancer at NHS England, said the health service remains committed to finding cancers earlier and will "explore every opportunity to detect more cancers sooner and save more lives." He indicated that NHS officials would study the trial data in detail before deciding what role, if any, Galleri might play in future cancer screening strategy. For now, though, the revolutionary blood test that was supposed to transform cancer detection in Britain has stumbled at the finish line, leaving the question of its value unresolved and its future uncertain.