Liquid Biopsy: A Distinctive Approach to the Diagnosis and Prognosis of Cancer

Abstract

Cancer is a leading cause of morbidity and mortality worldwide. Over the past decades, the concept of precision cancer medicine has emerged as a novel approach in the field of oncology that aims to tailor the most effective treatment options to each individual cancer patient based on the genetic profile of the tumor of each individual patient. Recently, tissue biopsy has become an essential part of cancer care and is widely used to characterize the tumor. However, tissue biopsy techniques face different challenges due to their invasiveness, cost, time, and adversity in potential sampling due to tissue heterogeneity. To overcome these issues, a non-invasive approach has developed, which is known as liquid biopsy. It is a simple, fast, and worthwhile technique based on the analysis of circulating tumor DNA (which is a fraction of cfDNA), circulating tumor cells (CTCs), and other tumor-derived material in blood plasma. This review provides an overview of the concept of liquid biopsy and briefly discusses the role of ctDNA and CTC analysis as tools for early diagnosis and prognosis of cancer. In this review, we also speculate on the advantages of liquid biopsy as opposed to tissue biopsy and postulate that liquid biopsy may be a comprehensive approach to overcome the current limitations associated with costly, invasive, and time-consuming tissue biopsy.

Keywords: Cancer; circulating tumor DNA (ctDNA); circulating tumor cells (CTCs); liquid biopsy; tissue biopsy.

Figure 1.

Cell-free DNA (cfDNA) concentration in healthy and cancer patients and its relation to circulating tumor DNA (ctDNA). ctDNA originates mainly from necrosis, apoptosis, and/or circulating tumor cells (CTCs). Fragments of this tumor-derived DNA circulate in the blood with cfDNA(derived from all types of cells, cancerous and noncancerous). A portion of this cfDNA can also come from live cells when they spontaneously release DNA.

Figure 2.

This is a schematic diagram showing the collection resource for genetic material from various gravitational layers of blood. The genetic material for liquid biopsy can be collected from various body fluids, including blood compartments, ctDNA from plasma, and CTC from buffy coat. Different types of change can be detected as tumor markers from CTC-derived RNA, such as oncogene expression and mutation. ctDNA can be used for the detection of mutations, the promotor methylation of tumor suppressor genes, and the length of DNA fragments.