Detection of Circulating Tumor DNA in the Blood of Cancer Patients: An Important Tool in Cancer Chemoprevention.

Liquid biopsies represent novel promising tools to determine the impact of clonal heterogeneity on clinical outcomes with the potential to identify novel therapeutic targets in cancer patients. We developed a low-coverage whole-genome sequencing approach in order to noninvasively establish copy number aberrations in plasma DNA from metastasized cancer patients. Using plasma-Seq we were able to monitor genetic evolution including the acquirement of novel copy number changes, such as focal amplifications and chromosomal polysomies. The big advantage of our approach is that it can be performed on a benchtop sequencer, speed, and cost-effectiveness. Therefore, plasma-Seq represents an easy, fast, and affordable tool to provide the urgently needed genetic follow-up data. Here we describe our method including plasma DNA extraction, library preparation, and bioinformatic analyses.