NHS-Galleri reports screening performance after trial missed primary endpoint

The NHS-Galleri randomized controlled trial evaluated a multi-cancer early detection (MCED) test added to usual care in 142,250 adults aged 50–77 years, allocated equally to intervention or control. This Nature Medicine report describes prespecified secondary test-performance endpoints among evaluable intervention participants across three annual screening rounds. Positive results prompted diagnostic workup through NHS standard-of-care pathways, informed by the predicted cancer signal origin.

Positive results occurred in 1.03%, 0.80% and 0.90% of participants in rounds 1–3, respectively. Overall, 937 participants had MCED-detected primary cancers. Cancer detection rates were 0.60%, 0.40% and 0.41%, while positive predictive values were 58.0%, 50.4% and 45.8%. Across rounds, specificity ranged from 99.50% to 99.60%, and negative predictive values ranged from 98.86% to 98.98%. Episode sensitivity was 26.7%–37.2% for all cancers and 47.6%–63.4% for 12 prespecified cancer types. Cancer signal origin accuracy was 91.1%–93.6%.

These results characterize screening performance within NHS pathways but do not establish clinical benefit. The analyses were descriptive, without hypothesis testing, and were restricted to intervention-arm test performance. Importantly, the trial’s primary endpoint—a reduction in stage III/IV cancer diagnoses in the intervention versus control arm—was not met, as reported separately.