A blood test capable of detecting more than 50 types of cancer, once hailed as a potential holy grail in oncology, has failed to achieve its primary objective in a large-scale clinical trial involving 142,000 NHS patients in the United Kingdom. The results were presented at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago, the world's largest cancer conference.
Trial Design and Primary Endpoint
The study aimed to assess whether adding the multi-cancer early detection (MCED) test, known as Galleri, to standard screening could shift cancer diagnoses to earlier, more treatable stages. The trial enrolled 142,942 participants aged 50 to 77 with no cancer symptoms. Each participant had blood drawn once a year for three years and received the recommended cancer screening tests. Half of the participants had their blood samples analysed using the Galleri test, while the other half served as the control group, with their blood not subjected to the test.
Those in the Galleri group who received a positive result underwent diagnostic follow-up with a doctor, as did all participants in both groups who developed cancer-related symptoms. The primary endpoint was a combined measure of stage three and stage four diagnoses in a pre-specified group of 12 cancers, comparing the Galleri test plus standard care versus standard care alone.
Results: No Statistical Reduction in Late-Stage Cancers
The findings revealed no statistically significant reduction in advanced cancers (stages three to four) among those who received the Galleri test compared with the control group. Dr Julie Gralow, ASCO's chief medical officer and executive vice-president, commented: "While the Galleri-NHS study results show some encouraging trends toward tumour downstaging, it is important to recognise that the trial did not statistically reduce late-stage cancers by its predefined primary endpoint."
One senior cancer figure who spoke to the Guardian on condition of anonymity was more blunt: "The trial flopped. Clear and simple."
Secondary Findings and Reactions
Despite missing the primary endpoint, Grail, the California-based company behind the test, highlighted other encouraging findings. Researchers noted a 14% reduction in stage four cancers alone, suggesting that the most deadly cancers were being detected at an earlier stage. Harpal Kumar, Grail's chief scientific officer and former chief executive of Cancer Research UK, said: "Galleri represents a potential transformational shift in cancer detection."
However, experts not involved in the trial expressed scepticism. Professor Richard Houlston, head of the division of genetics and epidemiology at the Institute of Cancer Research, London, stated: "This is the largest randomised trial so far to evaluate a multi-cancer early detection blood test. However, the researchers have presented their findings far more positively than the overall results justify. The study's main goal was to show a reduction in late-stage cancers overall, and this primary endpoint was not met. While some secondary findings are encouraging, in so far as a possible reduction in the most advanced cancers after repeated screening rounds, these results remain uncertain and should be interpreted cautiously."
He added: "The failure to meet the primary endpoint is the crux of the issue here. Mortality outcomes will be available in a couple of years, examination of which will be warranted. However, on the basis of results from this and smaller trials, there is no evidence base upon which to justify implementation of Galleri at a population scale."
Next Steps for the NHS
Professor Peter Johnson, the national clinical director for cancer at NHS England, said: "We look forward to seeing the data from the trial in detail, to help us make decisions on what this could mean for the NHS in the future." The trial's mortality outcomes are expected in a couple of years, which will provide further clarity on the test's potential benefits.
