[Cancer Early Detection by cfDNA Analyses].

The analysis of cell-free DNA (cfDNA) in blood is expected to serve as a new diagnostic method for early cancer detection and treatment monitoring by examining trace amounts of ctDNA derived from cancer cells. In cancer patients, ctDNA circulates in the bloodstream, and thanks to technological innovations in next-generation sequencing (NGS) and the analysis of fragmented DNA at low levels, it is now possible to non-invasively detect the presence and type of cancer. Multi-cancer early detection (MCED) is a method for detecting cancer early and identifying its specific type by analyzing cfDNA fragment characteristics, ctDNA somatic variants, and DNA methylation status; some MCED tests are already commercially available. However, when used as a standalone test, MCED faces challenges in early detection reliability and the risk of overdiagnosis, necessitating improvements in sensitivity and specificity, as well as clinical efficacy evidence. For this reason, MCED is currently positioned to complement existing screening methods. Furthermore, in addition to analyzing DNA fragment characteristics and methylation, machine learning is expected to enable more accurate detection. However, challenges remain, such as improving sensitivity in clinical stage Ⅰ and reducing false positives, making further research progress essential. Nevertheless, MCED holds great potential for personalized cancer prevention. This review discusses early cancer diagnosis using cfDNA analysis and the technological advancements in this field.