Liquid Biopsy: Is There an Advantage to Analyzing Circulating Exosomal DNA Compared to cfDNA or Are They the Same?

Cancer is one of the leading causes of death worldwide. This life-threatening disease requires novel strategies for the early detection and therapy response prediction. Circulating DNA was first described 70 years ago. However, only the recent evolution in the PCR-based sequencing techniques allow the minimally invasive molecular profiling of circulating mutant DNA from small-volume "liquid biopsies" such as blood, urine, or saliva. In this article, we aim to summarize the fast-growing evidence for cfDNA and exosomal DNA as minimally invasive diagnostic markers in solid tumors and to highlight their opposing diagnostic advantages and disadvantages.