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Jun 02, 2026
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Galleri Multi‑Cancer Blood Test Misses Primary Goal in Massive NHS Trial

AI Summary
A 142,000‑patient NHS trial of the Galleri multi‑cancer early detection blood test failed to meet its primary endpoint of reducing late‑stage cancer diagnoses. While a secondary analysis hinted at a 14% drop in stage‑four cancers, experts caution that the overall evidence does not yet support widescale rollout.

The world’s largest randomised trial of a multi‑cancer early detection (MCED) blood test, involving 142,942 NHS participants, did not achieve its main aim of cutting late‑stage cancer diagnoses, according to data presented at the ASCO annual meeting in Chicago.

Trial Overview and Primary Objective

The study enrolled adults aged 50‑77 with no cancer symptoms, assigning half to annual Galleri testing alongside standard screening and the other half to standard screening alone. Positive Galleri results triggered diagnostic follow‑up, mirroring the protocol for symptomatic participants in both arms.

Key Findings and Statistical Outcomes

  • Participants: 142,942 screened over three years.
  • Primary endpoint: Combined stage III and IV diagnoses across 12 pre‑specified cancers.
  • Result: No statistically significant reduction in advanced‑stage cancers in the Galleri arm versus control.
  • Secondary signal: Stage IV cancers fell by 14% in the Galleri group, a finding the company Grail highlighted as encouraging.

Dr Julie Gralow, ASCO’s chief medical officer, noted the trial showed “some encouraging trends toward tumour downstaging” but emphasized the primary endpoint was not met.

Implications for NHS Cancer Screening Strategy

Experts such as Prof Richard Houlston (Institute of Cancer Research) warned that the lack of a primary‑endpoint hit undermines any justification for nationwide adoption of Galleri. Prof Peter Johnson, NHS England’s national clinical director for cancer, said the NHS will scrutinise the full data before deciding on future implementation.

The trial’s outcome raises questions about the cost‑effectiveness of MCED tests at population scale and may temper enthusiasm for rapid integration into existing screening programmes.

Future Directions and Remaining Questions

Mortality outcomes, expected in the next few years, will be critical to assess whether earlier detection translates into survival benefits. Researchers and policymakers will likely await these results before committing to broader rollout, while Grail may refine its assay based on the secondary findings.