Promises and Pitfalls of Using Liquid Biopsy for Precision Medicine.

New sensitive assays are currently available for the detection of circulating tumor DNA (ctDNA) and circulating tumor cells (CTC). However, there remains a need for standardization of preanalytical issues and cross-platform comparison studies. Liquid biopsies are being evaluated for treatment selection, for monitoring disease response and resistance, for tracking minimal residual disease, and for cancer diagnosis. Multiple studies are underway to assess the clinical utility of CTC and ctDNA in different settings (treatment-naïve vs. resistant, adjuvant vs. metastatic) and for different treatment modalities (systemic therapy, surgery, radiation therapy). This review aims to map the challenges that remain to be addressed before liquid biopsies can be widely used for cancer management. ©2019 American Association for Cancer Research.