Grail’s large NHS-Galleri randomized trial failed to show a statistically significant reduction in late-stage (stage III–IV) cancer diagnoses, the company reported in top-line results. The study enrolled 142,000 people in England and compared standard-of-care screening with and without the Galleri multicancer early detection blood test. Grail highlighted pre-specified signals: fewer stage IV diagnoses and an increase in early-stage detections for a group of 12 high‑mortality cancers, and plans to extend follow-up by 6–12 months to see if effects emerge with more time. Investors reacted sharply: shares fell roughly half their value in after‑hours trading. The NHS trial outcome complicates Grail’s regulatory and commercial pathway in the U.K. and U.S.; the data will be presented at ASCO and will be scrutinized for statistical power, endpoint definitions, and how early-stage detection translates into mortality benefit. Multicancer early detection (MCED) tests screen for cancer-specific signals in blood—validation requires demonstrating reduced late-stage incidence or mortality, not just detection rates.