LIQUID BIOPSY FOR PATIENTS WITH CANCER: DIFFERENT APPROACHES AND CLINICAL APPLICATIONS
Treatment of cancer patients is now based on extensive analysis of cancer cells obtained by tissue biopsy. In addition to being invasive, tissue biopsy relies on analysis of single cancer sample in one time point, which may not be representative due to cancer heterogeneity and clonal evolution. Liquid biopsy is a minimally invasive test done on a sample of blood or other bodily fluid from a patient and it has potential to overcome these limitations of tissue biopsy. Liquid biopsy has been studied as potential diagnostic, prognostic and predictive marker in patients with cancer. Several limitations for wider application of liquid biopsy in routine clinical practice still remain, such as a lack of consensus on detection methods, an abundance of difficult to analyze sequencing information and so far little proof of clinical utility based on large clinical trials. Three most widely studied approaches to liquid biopsy in cancer patients are analysis of circulating tumor cells, circulating tumor DNA and exosomes. Each of these approaches has its advantages and limitations, which are discussed in this review. Focus of this review is on clinical studies analyzing potential clinical utility of liquid biopsy in treatment of patients with different types of cancer.