ctDNA (circulating tumor DNA) consists of small DNA fragments released into the blood by apoptotic and necrotic tumor cells. As the molecular arm of liquid biopsy, it reflects the tumor's genetic profile non-invasively.
cfDNA vs ctDNA
- cfDNA (cell-free DNA): all cell-derived free DNA in blood (including from healthy cells). Total DNA burden
- ctDNA: the tumor-derived fraction of cfDNA. Between 0.01% and 50% of total cfDNA may be tumor-related
When Should ctDNA Be Measured?
- Mutation detection: non-invasive detection of somatic mutations such as KRAS, EGFR, BRAF, TP53
- MRD assessment: detection of minimal residual disease after surgery/chemotherapy
- Resistance mutations: non-invasive detection of resistance mechanisms at progression
- Tumor burden: estimation of overall tumor burden from ctDNA concentration
Analytical Challenges
- Low ctDNA fraction: requires sensitive NGS methods (e.g. error-corrected sequencing)
- Plasma processing speed: cfDNA degradation makes plasma separation mandatory within 2–4 hours
- Standardization: pre-analytical variations can affect results
See our contact page for our ctDNA analysis support service.
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