funded by the Tata Memorial Centre, aims to investigate the utility of a liquid biopsy using cell free DNA (cfDNA) for monitoring response of breast cancer patients to therapy in the neo-adjuvant chemotherapy (NACT) settings. We have biopsied patients undergoing neo-adjuvant chemotherapy before the start of their therapy, and at the time of their surgical resection. We have also collected patients’ blood before every cycle of chemotherapy and isolated cfDNA from the plasma. We next aim to identify mutational markers in the cfDNA, specific to the tumour DNA (ctDNA) using custom next generation sequencing assays. We plan to co-relate these ctDNA biomarkers with the observed tumour burden during NACT and ask if they can be surrogate markers of response to NACT in breast cancer patients.