Clinical Circulating Tumor DNA Testing for Precision Oncology

Circulating tumor DNA (ctDNA) is the portion of the cell-free DNA in the blood of cancer patients released from tumor cells via apoptosis, necrosis, or active release. From 10 mL of blood, the 4–5 mL of plasma obtained from a cancer patient contains 5–10 ng/mL of ctDNA. The plasma contains not only ctDNA of tumor origin, but also DNA from normal cells or clonal hematopoiesis. Another characteristic of ctDNA is its rapid clearance from circulation; it has a half-life of 16 minutes to 2.5 hours. Obtaining reliable results from ctDNA requires the application and approval of standardized clinical validation guidelines; however, the status of numerous ctDNA tests currently varies. The clinical use of ctDNA testing should be carefully considered based on the test’s specific needs and characteristics. Here we provide the different characteristics of ctDNA tests and information regarding their validation and approval status.