Liquid Biopsy Using Cell-Free Tumor DNA for Gastrointestinal Cancers

Abstract

Since the advent of precision medicine in 2015, personalized genomic profiles of mutated DNA from tumor tissues have been applied for the selection of compatible drugs for the clinical treatment of genomic aberrations. As a more convenient and less invasive method of precision medicine, liquid biopsy that analyzes mutated cell-free tumor DNA (ctDNA) can be used as a biomarker for postoperative recurrence of genomic aberrations and their appropriate treatment. In this chapter, we explore liquid biopsies for gastrointestinal (GI) cancers in detail. We review the literature on ctDNA-related issues, including the mechanism of ctDNA identification in plasma, the methodology for identifying ctDNA in profiles and targeted sequencing assays, intratumor heterogeneity, recent technological innovations in ctDNA analysis in GI cancers, and the limitations of current approaches. We also describe the clinical aspects of GI cancer, such as actionable targets and clinical trials using mutated ctDNA analysis, the significance of longitudinal observation of ctDNA for clonal evolution after targeted therapy, and the detection of minimal residual disease by ctDNA analysis. Finally, we summarize a few recent studies on ctDNA in colorectal, gastric, and esophageal cancers. (192)