Monitoring of circulating tumor DNA in metastatic triple-negative breast cancer patients undergoing chemotherapy.

e22056 Background: Triple negative breast cancer (TNBC) is associated with aggressive histological features, high relapse rates, and poor overall survival. To improve the management of TNBC patients, there is an unmet need to develop noninvasive biomarkers to monitor treatment efficacy. TP53 mutations are clinically relevant in TNBC since they present in 60-88% of TNBC cases. Thus, circulating cell free tumor DNA (ctDNA) identified by TP53 mutations could serve as a “liquid biopsy” for TNBC tumors. In this study we measured the mutant TP53 fraction in ctDNA of metastatic TNBC patients by next generation sequencing (NGS) and compared our results to Circulating Tumor Cell (CTC) numbers. Methods: 36 women with metastatic TNBC and receiving a new line of systemic therapy were enrolled in this study. DNAs from 36 solid tumors and 56 plasma samples were extracted and amplified using a panel of target specific primers covering all the exons of TP53 and sequenced as described by the TAMSeq protocol. This method u...