Circulating Tumor DNA (ctDNA)
Type
Method / Biomarker
Description
Circulating tumor DNA (ctDNA) is the tumor-derived fraction of cell-free DNA (cfDNA) in the bloodstream. It carries tumor-specific mutations, copy-number alterations, methylation patterns, and fragmentation signatures that enable non-invasive monitoring of tumor evolution. ctDNA typically constitutes <1% of total cfDNA in early-stage disease and increases with tumor burden. Applications include minimal residual disease (MRD) detection, treatment response monitoring, resistance mutation identification, and phylogenetic tracking of subclonal dynamics. ctDNA is distinguished from normal cfDNA (predominantly hematopoietic in origin) and from clonal hematopoiesis (CH) variants that can confound interpretation.
Key metrics
- Typical fragment size: 167 bp (nucleosome unit)
- Half-life in circulation: minutes to 2 hours
- Detection sensitivity: as low as 0.003% VAF with tumor-informed assays
- Concordance with tissue: ~90% for clonal mutations
Wiki sources
- cfdna-vs-ctdna-explained — cfDNA vs ctDNA distinction
- asco-gu-2025-ctdna-next-generation — Epigenomic next-generation ctDNA technologies
- abbosh2017-ctdna-tracerx — Phylogenetic ctDNA tracking in NSCLC
- khatami2018-ctdna-personalized-medicine — ctDNA in personalized cancer therapy
- stejskal2023-ctdna-biology-review — ctDNA biology, release mechanisms, clinical relevance
- spina2018-ctdna-hodgkin-lymphoma — ctDNA in Hodgkin lymphoma
- wander2026-ctdna-cdk46-breast-cancer — ctDNA detection of CDK4/6 inhibitor resistance