GRAIL Presents Full Results from NHS-Galleri Trial at ASCO 2026

The randomized, controlled trial evaluated the Galleri multi-cancer early detection (MCED) blood test in England, enrolling 142,250 asymptomatic adults aged 50–77. Participants were assigned to receive Galleri in addition to standard screening or standard screening alone, with three blood samples collected approximately 12 months apart over two years.

The trial did not meet its primary endpoint of reducing combined Stage III–IV diagnoses across 12 prespecified cancers after three screening rounds (incidence rate ratio, 1.03; 95% CI, 0.92–1.14; p=0.6324). However, in a prespecified secondary endpoint, Stage IV diagnoses for these cancers decreased by 9% in round one, 22% in round two, and 26% in round three, resulting in an overall 14% reduction (incidence rate ratio, 0.86; 95% CI, 0.744–0.998; nominal significance). Similar reductions of 20% or greater were observed in rounds two and three across all stageable cancers.

Adding Galleri quadrupled screen-detected cancers and reduced clinically detected cancers after symptomatic presentation by 21%. Diagnoses made after emergency presentation declined by 25%. Stage I–II diagnoses in the 12 prespecified cancers increased by 16% across three screening rounds.

Performance metrics were consistent with prior studies: 1,801 participants (0.91%) had a positive result and 937 cancers were confirmed, yielding a cancer detection rate of 0.48% and an overall positive predictive value of 52.0% (58.0% in round one). Specificity was 99.55% (false positive rate 0.45%). Cancer Signal of Origin accuracy was 92.5%; episode sensitivity was 54.7% for the 12 prespecified cancers and 30.7% across all cancers. No serious related adverse events were reported, and the results will be submitted for peer-reviewed publication.

Galleri screens for more than 50 cancer types and is intended to detect cancer signals and predict where in the body the signal originated (Cancer Signal of Origin). The prescription-only test is intended for use alongside recommended screening. It is performed in a laboratory certified under the Clinical Laboratory Improvement Amendments (CLIA) and accredited by the College of American Pathologists (CAP), but has not been cleared or approved by the Food and Drug Administration (FDA).

“We saw a substantial decrease in Stage IV cancers, but this was outweighed by an overall increase in the number of Stage III cancers, particularly in the prevalent screening round. We believe the Stage III increase was driven in part by a number of Stage IV cancers being shifted to earlier stages, including at Stage III, and the fact that many more cancers overall were found earlier through screening in the intervention arm, while the equivalent cancers may not yet have been diagnosed in the control arm,” said Sir Harpal Kumar, Chief Scientific Officer and President of Global Clinical and Medical Affairs at GRAIL.

“We would expect to see more of these as yet undiagnosed late-stage cancers being found in the control arm with longer follow-up. In addition, the trial has revealed just how much undiagnosed and uninvestigated Stage III cancer is already prevalent in the population before any screening commences. Finding these cancers earlier means we can start treating those patients with the urgency needed and, in many cases, with the opportunity of curative intent,” said Kumar.

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