Liquid Biopsies: Genotyping Circulating Tumour Dna in Colorectal Cancer

Abstract

Genotyping tumor tissue in search of somatic genetic alterations for prognostic and predictive information has become routine practice in clinical oncology. While these sequence alterations are highly informative, tumor tissue is often difficult to obtain, represents a single snap-shot in time and is subject to significant selection bias. It has long been known that solid tumors release DNA in the blood and the load of circulating tumor DNA (ctDNA) has been correlated to staging and prognosis. However, only recent advances in the sensitivity and accuracy of DNA analysis have allowed for genotyping of somatic changes found in tumors by interrogating ctDNA (Liquid Biopsies). Applications of liquid biopsies to track tumor dynamics in real time and for the early detection of relapse will be discussed using colorectal cancer as a model system.