Early detection of multiple cancers: the era of methylation-based liquid biopsy.

Liquid biopsy based on circulating cell-free DNA (cfDNA) methylation has become a leading non-invasive strategy for multi-cancer early detection (MCED). Aberrant DNA methylation arises at the early stage of tumorigenesis and displays cancer-type-specific signatures, enabling early capture of tumor-derived epigenetic signals. High-throughput sequencing, digital PCR and machine learning algorithms have greatly improved the sensitivity and specificity of methylation-based assays. Large-scale clinical trials including CCGA, PATHFINDER, THUNDER and GUIDE have validated that MCED tests achieve high specificity (>99%) and reliable accuracy for tissue of origin prediction. Integrating methylomics with fragmentomics further boosts early detection performance, especially for early-stage tumors with low ctDNA shedding. Nevertheless, clinical translation still faces notable hurdles, including technical standardization, biological confounding factors, high cost and the demand for large-scale prospective mortality endpoint validation. Future development will rely on multi-omics integration, optimized bioinformatic pipelines and standardized interventional trials to lower cancer-specific mortality. In summary, methylation liquid biopsy is poised to reshape cancer screening from single-organ late diagnosis to multi-cancer early intervention, offering profound prospects for precision oncology.