ASCO said it will not recommend Grail’s Galleri MCED test for use in cancer screening after reviewing results from the NHS-Galleri randomized trial. The trial did not meet its primary endpoint of reducing the incidence of stage III and IV cancers across multiple tumor types, reigniting debate about evidence thresholds for population screening. ASCO’s decision leaves already-available early access programs in place, but it signals tighter professional guidance around guideline inclusion. ASCO chief medical officer Julie Gralow said the Galleri assay should not be included in screening guidelines while the primary endpoint miss stands. Grail’s clinical leadership argued that secondary observations—fewer stage IV cancers and more stage I and II detections after three years—support potential future role for MCED at scale. The disagreement between guideline standards and nuanced secondary outcomes is likely to affect adoption decisions by oncology practices and health systems.