Rising cell-free DNA level tracks cancer-associated methylation signal and improves multicancer detection.

Higher total circulating cell-free DNA in a multicancer cohort of 1,480 previously untreated participants is linked to enrichment of cancer-associated DNA methylation signatures, independent of cancer type and stage.

• Why it matters: Tumor-derived DNA is expected to be diluted by immune-derived fragments, but the study tests whether methylation signals instead track with total ccfDNA and whether this improves detection.
• What they did: Across 43 hospitals, the authors analyzed 14 cancer types at all stages, plus benign growths and healthy volunteers, relating total ccfDNA to methylation signature signal while adjusting for demographic, clinical, and technical covariates.
• The result: Total ccfDNA explains more variance in cancer-associated methylation signal than disease stage, and higher ccfDNA is associated with greater detection sensitivity (stage I: 0.55 to 0.85; stage II: 0.59 to 0.86), including in symptomatic benign lesions.

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