# MCED (Multi-cancer early detection) tests

Multi-cancer early detection (MCED) tests are blood tests. They scan the cell-free DNA floating in your plasma. They look mainly at two things: methylation patterns and the shapes of DNA fragments. The goal is to spot a shared 'cancer signal' across many tumor types, and to guess which tissue it came from. The most advanced is GRAIL's Galleri. It reads targeted methylation across more than 100,000 spots in the genome. In the PATHFINDER study (Schrag 2023), Galleri found a cancer signal in 1.4% of 6,621 adults aged 50 and over. Its specificity was 99.1%, and its positive predictive value was 38%. The earlier CCGA validation (Klein 2021) reported 99.5% specificity and 88% tissue-of-origin accuracy. Its overall sensitivity was about 51%, rising sharply with stage. SYMPLIFY (Nicholson 2023) showed a 75.5% positive predictive value in patients with symptoms. Galleri is sold in the US as a lab-developed test. GRAIL filed a PMA with the FDA on 29 January 2026. That filing drew on PATHFINDER 2, presented at ESMO in October 2025. The headline NHS-Galleri results (February 2026) missed their main stage-shift endpoint. But they showed fewer stage-IV diagnoses in a pre-specified subgroup of 12 deadly cancers. Watch the confounders: benign inflammation, a recent biopsy, pregnancy, and clonal hematopoiesis.

## Sources

- Schrag D, Beer TM, McDonnell CH, et al.. (2023). Blood-based tests for multicancer early detection (PATHFINDER): a prospective cohort study. Lancet. https://doi.org/10.1016/S0140-6736(23)01700-2
- Nicholson BD, Oke J, Virdee PS, et al.. (2023). Multi-cancer early detection test in symptomatic patients referred for cancer investigation in England and Wales (SYMPLIFY): a large-scale, observational cohort study. Lancet Oncology. https://doi.org/10.1016/S1470-2045(23)00277-2
- Liu MC, Oxnard GR, Klein EA, et al. (CCGA Consortium). (2020). Sensitive and specific multi-cancer detection and localization using methylation signatures in cell-free DNA. Annals of Oncology. https://doi.org/10.1016/j.annonc.2020.02.011

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_Canonical: https://longevity-china.com/en/glossary/mced-multi-cancer-detection · Part of Longevity Cities · Updated 2026-06-22_