Next generation sequencing will be performed on core biopsies of all enrolled patients for tumor-specific mutations (TSM) discovery. Based on those findings, droplet digital PCR (ddPCR) on plasma DNA samples will also be performed to confirm the presence of the TSM in the plasma on diagnosis, and one TSM will be chosen to track as the plasma tumor DNA (ptDNA) mutation of interest. Investigators will perform ddPCR on pre-operative plasma DNA samples and will assess for the presence of ptDNA. Pathologists will assess surgical specimens for pathologic response (such as complete response/pCR and residual cancer burden/RCB). As primary endpoint, investigators will assess the number of patients with and without preoperative ptDNA who have pCR versus residual disease. As exploratory endpoints, the following will also be performed: (a) quantitative multiplex methylation-specific PCR (QM-MSP) in diagnostic biopsy and definitive residual surgery specimen; and, (b) the circulating methylated tumor DNA (cMethDNA) assay in plasma specimens (baseline and after NAT), and evaluate associations with pathologic response.