ESMO: Grail's data on cancer blood test firms up

Results from the PATHFINDER 2 trial of Grail's blood test for multiple cancers have shown greater efficacy and a lower rate of false alarms than in an earlier trial of the technology.

The Galleri multi-cancer early detection (MCED) test – which looks for around 50 different types – achieved a seven-fold increase in cancer detection when added to standard screening tests for breast, cervical, colorectal, and lung cancers, according to the data, which was presented at the ESMO 2025 cancer Congress.

Moreover, around three-quarters of the cancers detected using Galleri – which looks for fragments of tumour DNA circulating in peripheral blood – have no currently recommended screening tests available, promising broader reach for detection programmes if it gets approved for use.

The study was carried out in 25,000 adults, without any symptoms of cancer, in the US and Canada over a 12-month period, with just under 1% of them getting a positive result. Of these, nearly two-thirds (62%) were confirmed by follow-up testing, which is a much higher rate than the approximately 43% seen in the prior PATHFINDER study of the MCED.

That still means that in almost 40% of cases the test delivers a false positive, but lead investigator Nima Nabavizadeh of Oregon Health & Science University noted that Galleri correctly ruled out cancer in 99% of those who tested negative. It also correctly identified the origin of the cancer in around 90% of cases.

"Cancer screening saves lives, but we routinely screen for just four or five cancer types in the US today and approximately 70% of cancer deaths come from cancers that do not have standard-of-care screening and are typically caught too late," he pointed out.

In PATHFINDER 2 more than half (54.5%) of detected cancers were in the early stages (1 or 2) and 69.3% were stage 3.

"Data from PATHFINDER 2 show that Galleri could fundamentally change our approach to cancer screening, helping to detect many types of cancer earlier, when the chance of successful treatment or even cure are the greatest, added Nabavizadeh.

Grail said that data from the study will be submitted to the FDA as part of the Galleri premarket approval (PMA) application, along with the results of a three-year trial involving 140,000 NHS patients in the UK, which is due to be published next year. It hopes to complete the marketing application in the first half of 2026.

Some scientists think that the test is not ready for a wide rollout, however. Prof Anna Schuh, a specialist in molecular diagnostics at the University of Oxford, who said that the 62% detection rate "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."

Prof Schuh said that the 133 cases of cancer detected in PATHFNDER 2 is well lower than might be expected and below what would probably be needed to meet a cost-utility analysis for the NHS, based on an anticipated list price of $996 per test.

"Based on this data, does this test in this specific unselected cohort (i.e., not enriched for cancer risk) represent good value for taxpayers’ money if it picks up only a third of the people with cancers in this cohort and of these a quarter are cancers that could be picked up with conventional screening?" she asked.

California-based Grail was formerly part of DNA sequencing giant Illumina, which bought the company for $7.1 billion in 2020, but was divested last year after the takeover was challenged by antitrust regulators.