Liquid Biopsy in Cancer Patients by Antonio Russo Antonio Giordano & Christian Rolfo

Author:Antonio Russo, Antonio Giordano & Christian Rolfo
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Circulating Tumor DNA (ctDNA)

The investigation of ctDNA can hypothetically reveal a wider genomic landscape of a tumor [33]. For this purpose, new sensitive technical approaches are available to analyze EGFR mutational status from plasma-derived ctDNA . In particular, digital PCR (dPCR) and next-generation sequencing (NGS ) platforms represent to date the most studied approaches for application in clinical practice. Through the dPCR approach, the DNA sample is partitioned into thousands of single PCR reactions. As in the qPCR approach , analysis software allows to identify a positive or a negative signal indicating the presence or absence of a target sequence. Therefore, a mutated ctDNA can be detected in a wide background of wild-type sequences [34]. The introduction of NGS technologies in clinical practice is the most important revolution that we have experienced since the discovery of polymerase chain reaction (PCR) and Sanger sequencing . Until now we have been working analyzing one gene at a time and one patient at a time, with NGS techniques this assertion has been revolutionized and we can analyze multiple genes and multiple patients at a time with a consistent reduction in time and costs [35]. NGS is a high-throughput technique, based on massive parallel sequencing of thousands of DNA molecules [36]. There are several NGS platforms that differ mainly in the detection chemistry, but they all share some important steps: library preparation, library amplification, sequencing, and data analysis. At the end of the analysis they all provide a plethora of information about the mutational landscape of the analyzed samples that can be used in clinical practice. Another great advantage of NGS compared to Sanger sequencing is the higher sensitivity, which is important when we have to look for somatic and rare mutations. This is the case of liquid biopsy and specifically of circulating tumor DNA (ctDNA) analysis. The information arising from ctDNA analysis will broad from early diagnosis to prognosis as well as response to drug administration and real-time monitoring of the disease.

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