Opinion: H. Gilbert Welch argues FDA should reject Grail's Galleri multi-cancer screening test

Writing in STAT News, physician and researcher H. Gilbert Welch argues that the FDA should not approve Grail's Galleri multi-cancer early detection test. Welch, a longstanding commentator on cancer screening science, contends that the available evidence does not demonstrate that the test reduces cancer mortality — the outcome that matters most for any population-level screening programme.

Welch's central argument is that detecting more cancers at earlier stages is not itself a measure of benefit. He points to the risk of overdiagnosis — identifying cancers that would never have caused harm — and the potential for a cascade of follow-up investigations, anxiety, and procedures in people whose signal does not ultimately prove to be cancer. He frames the approval question around a principle he attributes to the screening science community: progress means fewer people dying from cancer, not more people being told they have it.

This opinion piece is contextually relevant to the genetics community because Galleri is a circulating tumour DNA (ctDNA) methylation-based liquid biopsy, and its proposed positioning as a population screening tool touches directly on questions of analytical validity, clinical validity, and clinical utility that are central to genomic medicine evaluation frameworks. The piece follows an FDA advisory panel's endorsement of Galleri reported by Genetic Current on 24 September 2026. The views expressed are those of the author and do not represent the editorial position of Evagene or Genetic Current.