NHS-Galleri Trial Misses Primary Endpoint; Shows Reduction in Late-Stage Cancer
GRAIL's NHS-Galleri trial missed its primary endpoint of reducing combined Stage III and IV cancer diagnoses. However, the trial showed a 26% reduction in Stage IV diagnoses by the third screening round. Results were presented at ASCO 2026, and GRAIL stock fell following the announcement.
GRAIL announced detailed results from the landmark NHS-Galleri trial, which failed to meet its primary endpoint of reducing combined Stage III and IV cancer diagnoses but demonstrated significant decreases in Stage IV cancer in subsequent screening rounds. The randomized controlled trial evaluated annual screening with the Galleri multi-cancer early detection test in 142,250 participants in England's National Health Service.
The NHS-Galleri trial assessed a combined primary endpoint of Stage III and IV diagnoses in a pre-specified group of 12 cancers when the Galleri test was added to standard of care screening versus standard of care alone. There was no statistically significant difference within a 1-year follow-up window after the last appointment. However, Stage IV cancer diagnoses decreased sequentially with each year of screening, showing a 9% reduction in the first "prevalent" screening round, a 22% reduction in the second round, and a 26% reduction in the third round for the 12 pre-specified cancers. Overall, a 14% reduction in Stage IV cancers was observed, which was nominally statistically significant.
When added to standard of care screening, the Galleri test increased the cancer detection rate four-fold and increased Stage I-II cancer diagnoses by 16%. The test also reduced cancer diagnosis through emergency presentation by 25%. The trial revealed that the increase in Stage III cancers, particularly in the prevalent screening round, was driven partly by Stage IV cancers being shifted to earlier stages and by many more cancers being found earlier through screening in the intervention arm.
The results were presented at the 2026 American Society of Clinical Oncology Annual Meeting. Following the announcement, GRAIL stock plummeted. The inconclusive results could reduce the chance of a large NHS program, insurance coverage, and weaken the likelihood of FDA's PMA approval of Galleri. The Galleri test is expected to continue growing in 2026, improving GRAIL's revenue outlook, but major revenue scale still likely relies on FDA approval or other developments.