Circulating tumor DNA (ctDNA)

Circulating tumor DNA (ctDNA) refers to extracellular DNA shed or released into the circulation by tumor cells through apoptosis or necrosis. It exists in cell-free form and is found in body fluids such as blood, synovial fluid, and cerebrospinal fluid. ctDNA comprises single-stranded or double-stranded DNA, as well as a mixture of both, in the form of DNA-protein complexes or free DNA. The level of ctDNA reflects a comprehensive landscape of tumor-related genomic alterations, including mutations, deletions, insertions, rearrangements, copy number variations, and methylation. Additionally, ctDNA has a short half-life, accurately reflecting the current status of tumors. Detection of ctDNA provides traceable information related to tumors, offering clinical prospects in tumor screening, early diagnosis, residual disease detection, recurrence monitoring, treatment efficacy assessment, guidance for targeted drug use, and survival evaluation. Compared to protein markers, ctDNA detection has minimal false positives, as ctDNA originates from genomic mutations in tumor cells.