Circulating tumor DNA (ctDNA) originates from tumor cells. It is a part of cell-free DNA that is distinguishable by characteristics present in the parent tumor, such as methylation mutations, copy number variations, and presence of specific biomarkers. Increasingly, ctDNA has been used in liquid biopsies to diagnose, treat, and monitor cancer. Find more details on ctDNA and how it is used in oncology here.
While liquid biopsies using ctDNA has distinct advantages over traditional biopsy methods, such as being noninvasive and cost-effective, it also has certain limitations.
Figure 1: Three theorized methods of ctDNA origination from tumors.