Blood-Based Diagnostics in Solid Tumors: An Overview

The application of patient-specific genetic information and molecular tumor characteristics enables the selection of treatment strategies for individual patients, improving the therapeutic efficacy and expanding the scope of personalized medicine. Emerging evidence from clinical research provides demonstration that the genetic landscape of any given tumor will dictate its sensitivity or resistance profile to anticancer agents. Nevertheless, the inter-and intra-tumor genetic heterogeneity can be a substantial impediment to the successful clinical application of this approach. Since acquired drug resistance is common during the course of the disease, there is an urgent need to monitor tumor evolution. On these bases, the importance of molecular re-characterization of metastatic disease has been prospectively confirmed and has been recently acknowledged in the clinical guidelines for the management of advanced malignancies. Nevertheless, obtaining serial samples of metastatic tissue is impractical and complicated by spatial heterogeneity, sampling bias, and invasive procedures. An attractive alternative to overcome these limitations is represented by the analysis of peripheral blood sample as a “liquid biopsy.” Blood draws can easily be performed serially; thus blood would be an ideal compartment for detection of prognostic and predictive biomarkers. Nowadays, the principal sources for liquid biopsies are represented by cells and intracellular materials that are released by the tumor mass and are swept away by the bloodstream, such as CTCs, ctDNA, and exosomes. This book provides an overview of the technological approaches to perform and enhance the strategy and the principal applications in clinical practice of “liquid biopsy.”