Imaging and repeated biopsies are currently used to monitor a tumor’s response to treatment and detect tumor mutations associated with acquired resistance to therapy. These approaches pose health risks to patients and are expensive and therefore performed less frequently. They also have limited sensitivity to detect small tumors, intra-tumor heterogeneity, tumors in locations that are difficult to image or biopsy, and micro-metastases. Recent studies have demonstrated that tumor cells release fragmented genomic DNA into the blood, which is stable in circulation. The ability to detect this cell-free circulating tumor DNA in blood provides the opportunity to develop non-invasive tests to measure tumor burden and detect molecular signatures in tumors that are associated with resistance to therapy. We are developing targeted next-generation sequencing assays to quantify tumor-specific DNA methylation and somatic mutations in blood plasma samples from breast cancer patients that can be used to monitor patients’ responses to therapy.
