Galleri blood test 'feasible at scale' on NHS despite missing primary goal

A blood test designed to catch multiple cancers before symptoms emerge has cleared a crucial hurdle: it can work at scale within the NHS. But the trial's path to that conclusion was more complicated than its developers had hoped.

The Galleri test works by detecting fragments of cancer DNA floating in the bloodstream—the earliest whisper of disease. Over three years, researchers enrolled 142,942 people aged 50 to 77 with no cancer symptoms across the UK. Half of them had blood drawn annually and tested with Galleri; the other half served as a control group. The trial was designed to answer a straightforward question: would this test, used alongside existing NHS screening programs, reduce the number of people diagnosed with advanced cancers?

In February, the test's developer Grail announced the trial had failed to meet its primary endpoint. The reduction in late-stage cancers overall was not statistically significant. It was a setback that could have ended the conversation about whether the NHS should adopt the test. Instead, when the full results were presented at the American Society of Clinical Oncology meeting in Chicago, a more nuanced picture emerged. The test had not worked as hoped in the first year of screening—a 9% reduction in advanced cancers. But in years two and three, the results shifted. Among 12 pre-specified cancer types responsible for two-thirds of cancer deaths in England, the test reduced the most advanced diagnoses by 22% and 26% respectively. Overall, the trial found 14% fewer stage 4 cancers and 19% more cancers caught at earlier stages.

The distinction matters because many of those 12 cancer types—ovarian, pancreatic, and others—have no organized screening programs in the UK. They are typically discovered late, when treatment options narrow and survival rates plummet. For these cancers, the Galleri test offered something new: a way to find them before symptoms forced people into emergency rooms. The trial showed that four times more people were diagnosed through screening rather than emergency presentation, and 25% fewer patients arrived at diagnosis through emergency settings.

Yet the miss on the primary endpoint has created a credibility gap. Professor Richard Houlston, head of genetics and epidemiology at the Institute of Cancer Research in London, said the researchers had presented their findings "far more positively than the overall results justify." The study's main goal was unmet, he noted, and the secondary findings, while encouraging, remained uncertain and should be interpreted cautiously. Julie Gralow, chief medical officer of the American Society of Clinical Oncology, acknowledged the tension: the trial showed "some encouraging trends toward tumour downstaging" but did not achieve its predefined primary goal of statistically reducing late-stage cancers overall.

What happens next depends on longer-term follow-up data and results from the Reach study, a separate trial testing Galleri on about 50,000 US patients. The UK National Screening Committee will weigh the evidence before deciding whether to implement the test in NHS services. Cancer Research UK emphasized that the government must also invest substantially in staff and infrastructure—cancer services already face persistent shortages, and if multi-cancer tests are deployed, referrals for suspected cancer could rise sharply. A Department of Health and Social Care spokesperson said the government welcomed the research and would make decisions based on evidence and patient benefit, but the path forward remains open and contingent on what the data ultimately shows.