Circulating cell-free DNA

Abstract

The analysis of cell-free circulating DNA (cfDNA) from blood is called liquid biopsy. cfDNA in blood constitutes a mixture of DNA released from cells from different tissues of the body. Liquid biopsy allows for detection of DNA in different aspects such as quantity, chromosomal alterations, sequence mutations and epigenetic changes. Circulating tumor DNA (ctDNA) can be obtained from the plasma or serum of cancer patients and provides a suitability for non-invasive sampling of tumor DNA. The ctDNA is a very promising tool and might be beneficial for early detection of cancer, identification of minimal residual disease, guidance for treatment and monitoring treatment response and tumor evolution. Invasive tissue biopsies are not suitable for continuous monitoring of tumoral changes during course of the disease. When analysis of ctDNAs in cancer patients is compared to the conventional physical and biochemical methods, blood-based ctDNA detection offers a non-invasive and easily applicable tool for cancer diagnosis and follow up, identification of molecular targets for cancer therapy, monitoring of tumor molecular profile in real time, detection of emerging molecular aberrations associated with resistance to a particular therapy and diagnosis of metastasis. This chapter focuses on the origins, structures and the clinical application of cfDNA/ctDNA.