PS4-2 PD-1 blockade as curative intent therapy in mismatch repair deficient locally advanced rectal cancer

Neoadjuvant chemotherapy and radiation followed by surgical resection of the rectum is a standard treatment for locally advanced rectal cancer. A subset of rectal cancer is mismatch repair deficient. Since mismatch repair deficient colorectal cancer is responsive to PD-1 blockade in the metastatic setting, we hypothesized that locally advanced mismatch repair deficient rectal cancer is sensitive to checkpoint blockade and may alter the requirements for chemoradiotherapy and surgery.