Abstract
Circulating tumor DNA (ctDNA), which is the cell-free DNA released from dying cancer cells into the blood, is an emerging topic in cancer research. ctDNA is expected to gain importance in a large range of diagnostic applications, from early detection to disease progression monitoring. Unlike research involving other biomarkers such as microRNA, where the focus is on the exploration of new marker molecules, research involving ctDNA is mostly focused on the development of analytical technologies. These technologies are classified into those based on mutation-enriched PCR and those based on digital PCR (for example, BEAMing). Because it allows quantitative assessments, digital PCR is becoming the method of choice. Among devices that rely on digital PCR technology, massively parallel DNA sequencers are notable because of their ability to produce large amounts of data. For such sequencers, the current technical obstacle is the high read error rate. Barcode technology can eliminate read errors by using consensus reads generated from multiple sequence reads of a single molecule and enables the de novo detection of mutations, thus eliminating the requirement to screen mutations in primary tumors.
