NHS poised to reject 'holy grail' cancer blood test despite fourfold detection boost

The NHS is preparing to reject a nationwide rollout of a blood test that quadrupled cancer detection rates, a decision that hinges on a narrow but consequential measure of success. The Galleri test, developed by US firm Grail, can identify more than fifty types of cancer by searching blood samples for fragments of tumor DNA. In a trial involving 142,250 people aged fifty to seventy-seven, the test found 937 cancers over three years, compared to 290 detected through standard NHS screening alone. Yet despite this fourfold increase in overall detection, health officials have concluded the test is not ready for the health service.

The trial's central problem was not what the test found, but when it found it. Among the roughly 71,000 participants receiving standard screening, eight percent of cancers were caught. That figure jumped to thirty-three percent in the group using Galleri. The test proved particularly effective at identifying stage four cancers—the most advanced, often incurable form—reducing diagnoses at that stage by fourteen percent. It also cut the number of cancer cases first discovered in accident and emergency departments by a quarter, a significant marker since such diagnoses typically indicate disease already far advanced. For specific cancers like prostate, ovarian, and bowel tumors, the test showed genuine promise.

But the trial failed to meet its primary target: shifting enough diagnoses to earlier stages to justify the cost and complexity of a national program. While early-stage diagnoses increased by sixteen percent, the test did not sufficiently reduce stage three cancers—those that have spread beyond their original site but remain potentially treatable. In the first year of the trial, stage three diagnoses actually rose by nineteen percent among test users, a result that investigators attributed to the test's initial learning curve. Performance improved in subsequent years, with reductions of five percent in year two and twelve percent in year three, but the damage to the trial's overall findings was done.

The decision to reject rollout reflects a hard calculation within the NHS: detecting more cancers is not the same as detecting them early enough to meaningfully change outcomes. Cancer experts have noted that without evidence the test improves survival rates—the ultimate measure of screening success—the health service cannot justify deploying it across the population. An insider involved in the trial told journalists there was "no chance" of a national rollout. The National Screening Committee reinforced this skepticism by simultaneously rejecting calls for a prostate cancer screening program using PSA testing, signaling a broader caution about unproven screening approaches.

Yet the story is not settled. Sir Harpal Kumar, Grail's chief scientific officer, argued that the test's success in reducing stage four diagnoses should translate into substantial survival improvements, even if those gains have not yet been measured. He noted that catching prostate cancer before stage four reduced incurable diagnoses by twenty-five percent, and emphasized that early detection matters most for cancers typically found late—liver, ovarian, pancreatic tumors where treatment options narrow sharply once disease advances. Professor Peter Sasieni, one of the trial's investigators, suggested the data could strengthen within twelve months, potentially reversing the NHS position. He pointed out that screening programs have historically taken a decade to roll out once evidence of benefit became clear.

The test was central to Labour's National Cancer Plan, unveiled by former health secretary Wes Streeting as part of a broader effort to improve Britain's cancer survival rates. Results from the £150 million trial were presented at the American Society of Clinical Oncology's annual conference, the world's largest gathering of cancer researchers. US regulators are expected to approve the technology next year, potentially creating pressure on the NHS to reconsider. Professor Peter Johnson, the national clinical director for cancer at NHS England, said the health service would "explore every opportunity" to detect cancers sooner, pointing to successes like the lung cancer screening program that has identified ten thousand cases, most at early stages, using mobile testing units in supermarket car parks and football grounds.

The disagreement among experts reflects genuine uncertainty about what the trial actually proved. Professor Richard Houlston, head of genetics and epidemiology at the Institute of Cancer Research, said researchers had "presented their findings far more positively than the overall results justify." But others, including Sasieni, believe the test's trajectory suggests it will eventually demonstrate clear benefit. The NHS will review the full trial data in detail before making a final decision, but the initial verdict is clear: detecting cancer four times more often is not enough if those detections do not arrive early enough to change how the disease is treated and how patients survive it.