Analysis of cell free DNA(cfDNA), unlike tissue biopsy, presents a new tool for the monitoring and treatment of cancer. The investigators have developed a differentiated sequencing assay, Digital Sequencing Technology (DST) that enables detection of rare genomic abnormalities with ultra high-specificity and sensitivity. The investigators assay is able to eliminate the error and distortion created by sample-prep and sequencing processes in standard NGS(next-generation sequencing ) workflows and produce near-perfect representations of all rare variants.