A major U.S. study has found that Galleri, a multi-cancer early detection (MCED) blood test currently being trialled by the NHS, correctly identifies cancer in 62% of cases where it detects a potential “cancer signal.” The simple blood test, which screens for more than 50 types of cancer, could mark a major step toward earlier, easier, and more accessible detection—often before symptoms appear.
The Galleri test, developed by U.S.-based biotech company Grail, detects fragments of tumour-derived DNA circulating in the blood, identifying the unique “fingerprints” of cancer. Unlike traditional screenings that focus on specific cancers, Galleri can scan for dozens of deadly types through a single annual blood draw.
Findings from the Pathfinder 2 trial, presented at the European Society for Medical Oncology (ESMO) Congress in Berlin, demonstrate that Galleri is highly accurate in ruling out cancer among healthy individuals while detecting many cancers at an early, more treatable stage.
Of those with a “cancer signal” in their blood, 61.6% were later confirmed to have cancer. In 92% of cases, the test also identified the organ or tissue of origin, reducing the need for multiple scans or invasive diagnostics. More than half of the newly detected cancers (53.5%) were stage I or II, while 69.3% were caught between stages I and III. Importantly, Galleri also correctly ruled out cancer in 99.6% of people who were cancer-free.
“We’re really very excited and we think this is a further step along the way in really transforming cancer outcomes,” said Sir Harpal Kumar, President of International Business and BioPharma at Grail, and former head of Cancer Research UK.
The Pathfinder 2 trial enrolled over 23,000 symptom-free participants from the U.S. and Canada, following them for at least 12 months. Results showed that combining Galleri with routine cancer screening led to a seven-fold increase in cancers detected within a year. Among 216 people with a positive “cancer signal,” 133 were later diagnosed with cancer—confirming the test’s 61.6% positive predictive value.
Sir Harpal explained:
“What we wanted to assess was, what added value does the test provide over and above existing screening? And one of the most important and exciting results is the fact that it detected seven times as many cancers as the other screening programmes put together.”
He added that Galleri could particularly benefit detection of hard-to-diagnose cancers such as pancreatic, head and neck, liver, ovarian, and others, where no standard screening exists.
“Assuming we do get positive results from NHS Galleri, the opportunity to find substantially greater numbers of cancers before they present clinically means we should be able to find a lot more of them at an earlier stage,” he said. “This opens up the possibility we can use more effective treatments and, in many cases, curative treatments. That should make a substantial difference to cancer outcomes.”
The test’s ability to pinpoint the tumour’s origin also makes the diagnostic process faster and more efficient, particularly for patients with vague or overlapping symptoms.
“If somebody presents with abdominal pain, you might ask: is this ovarian cancer, pancreatic cancer, colorectal cancer – or is it not a cancer at all? If we can help clinicians direct those investigations, then we can make much better use of what is very scarce diagnostic capacity,” Sir Harpal noted.
Experts suggest that Galleri could be introduced as an annual blood test for individuals aged 50 and above, when cancer risk rises significantly.
“Our analysis would suggest it’s going to be more cost effective from age 50 upwards,” Sir Harpal said, adding that some younger people—such as those with a prior cancer history or genetic risk—may also benefit.
A recent BMJ Open analysis found that annual MCED testing could reduce late-stage diagnoses by 49% and cancer deaths by 21% over five years compared to usual care.
Josh Ofman, President at Grail, said:
“These results are extremely compelling as approximately three-quarters of the Galleri-detected cancers do not have recommended screening tests today.”
However, some scientists have urged caution until long-term data on mortality reduction becomes available.
Professor Clare Turnbull, from the Institute of Cancer Research, London, said further data was needed to confirm whether Galleri truly reduces cancer death rates.
Professor Nitzan Rosenfeld, Director of the Barts Cancer Institute, described the results as “impressive,” noting that the 62% accuracy rate is “very encouraging and provides strong evidence that this test could be safe and informative.”
He added:
“Importantly, more than 50% of the cancers detected by the Galleri test in this study were early stage (stages I-II), and more than 75% of them do not have common screening options.”
Professor Anna Schuh, from the University of Oxford, offered a more cautious interpretation:
“The likelihood that an individual with a positive test result actually has cancer is about 60%. Or in other words: almost half of the time, the test gets it wrong when it calls a positive result. This is disappointing as it is only fractionally better compared to tossing a coin, although better compared to current screening tests where still most positive results turn out to be nothing.”
She added that while the test showed good sensitivity (74%) for common cancers, it performed less effectively (40%) for rarer types, which make up more than half of all cancers.
The upcoming NHS Galleri trial results, expected mid-2026, will be crucial in determining whether the test can be integrated into national screening programs—and whether this so-called “holy grail” of cancer detection can truly reshape early diagnosis and survival worldwide.
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