Data presented at ASCO show Galleri detected more early-stage cancers than all existing UK screening programs combined and sharply increased diagnoses in a US real-world study; researchers stress it does not replace standard screening and survival benefits remain unprovenA single blood test identified more early-stage cancers than all existing screening programs in Britain combined. In a second study, conducted among 36,000 people in real-world conditions, the test increased the number of cancer diagnoses by 6.5 times, most of them at stages still considered potentially curable.The two studies on Galleri, a blood test designed to detect signs of more than 50 types of cancer, were presented in recent days at ASCO, the American Society of Clinical Oncology’s annual meeting in Chicago.2 View gallery A single blood test identified more early-stage cancers than all existing screening programs in Britain combined (Photo: Grail)The technology behind Galleri is based on a relatively simple principle: cancerous tumors release fragments of cell-free DNA into the bloodstream, carrying distinctive molecular patterns. Analyzing those patterns is intended to detect a biological signature that may indicate the presence of a tumor and point to where in the body it originated. A positive result, however, is not a cancer diagnosis, but a signal that further medical evaluation is needed.The NHS-Galleri trial was conducted in England in cooperation with Britain’s National Health Service and included 142,250 participants aged 50 to 77 who had no symptoms suggesting cancer. Participants were randomly divided into two groups: one underwent standard screening only, while the other received standard screening plus an annual Galleri test over three screening rounds.The trial was designed to examine whether adding the test would reduce diagnoses of advanced stage 3 and 4 cancers among 12 predefined deadly cancers, including pancreatic, ovarian, liver, lung and colorectal cancers, as well as lymphoma.The results showed a significant shift in diagnosis patterns. After three screening rounds, stage 4 diagnoses among the 12 predefined cancers dropped by 14%, with the effect strengthening over time: 9% in the first round, 22% in the second and 26% in the third. Adding Galleri also led to a fourfold increase in cancers detected through proactive screening and a 16% rise in diagnoses at stages 1 and 2.Across all cancer types, there were 21% fewer diagnoses following the appearance of symptoms and 25% fewer diagnoses following urgent referral or emergency room visits.Of 1,801 participants who received a positive result, 0.91% of those tested across the three rounds, 937 were later diagnosed with cancer. The test’s positive predictive value was 52%, its specificity was 99.55%, and its accuracy in identifying the cancer’s origin in the body was 92.5%. Sensitivity stood at 54.7% for the 12 predefined cancers and 30.7% across all cancers, underscoring that the test is not meant to replace existing screening programs.The main caveat: the trial’s primary endpoint, a combined reduction in stage 3 and 4 diagnoses, did not reach statistical significance.Prof. Eric Klein, a senior scientist at Grail who attended the conference, said the findings should be viewed in a broader context. In the control group, which received only standard UK screening, 290 cancers were detected through screening.Prof. Eric Klein,Photo: Grail“When Galleri is added to existing screening programs, another 937 cancers are found that would not have been detected through standard screening alone,” he said. “That is why we see a fourfold increase in the number of cancers detected through screening.”Klein pointed to another finding he said has not received enough attention: Galleri alone detected 366 stage 1 or 2 cancers. By comparison, all existing screening programs in Britain combined detected 290 cancers, at all stages.2 View gallery Galleri looks for fragments of tumor DNA released into the bloodstream, which carry distinctive molecular patterns. Analyzing those patterns can signal a possible cancer and help identify where in the body it began (Photo: Grail)“So the claim that tests of this kind are not sensitive enough for early-stage cancer does not reflect the full picture,” he said. “At the population level, Galleri found more stage 1 and 2 cancers than all existing screening programs combined.”“When cancer is found at stages 1 through 3, it is often possible to offer treatment that is less aggressive, less expensive, requires less time away from family and work, and has a higher chance of cure,” Klein added.Prof. Ido Wolf, head of oncology at Tel Aviv Sourasky Medical Center and dean of the medical school at Tel Aviv University, who also attended the conference, said the findings should be read in light of changes in cancer care over the past decade.“When the trial was planned many years ago, stage 3 was much closer to stage 4 in terms of prognosis,” he said. “Today, things have changed completely. In lung cancer, stomach cancer, melanoma and other cancers, immunotherapy and biological treatments can be given at these stages, and sometimes they can downstage the disease and even cure it. If the trial were designed today, stage 3 and stage 4 might have been separated differently.”Prof. Ido WolfPhoto: Sourasky Medical Center