CTCs and ctDNA: Two Tales of a Complex Biology

A significant interest in the emerging liquid biopsy technologies has been driven by new tools for analysis of nucleic acids and alterations that are associated with cancer. As is so often the case, the gains from new technology come not from the technology itself but from the improved understanding of the biology. Using these tools, data on the detection of tumor-derived cells and tumor-derived fragmented DNA in a blood sample has focused much energy on developing sustainable validated protocols to analyze these samples. The emerging data on cell-free and cell-derived molecular templates supports a complementary analysis of these compartments depending on the sensitivity requirements, nature of the genetic alteration, biomarker needs, and clinical evidence required.