Neoplasms, Colon

The main goal of this study is to test a new treatment approach for colon cancer. The treatment involves dostarlimab along with a specific type of chemotherapy called CAPEOX (short for "capecitabine + oxaliplatin") to check if using these two together works better than using just CAPEOX by itself. This treatment is given before any surgery takes place; a method referred to as "neoadjuvant therapy." . The aim is to see if this new approach can show early signs of effectiveness in treating participants with a specific type of colon cancer known as mismatch repair proficient/ microsatellite stable (MMRp/MSS), where the cells have normal repair systems and stable DNA sequences. This study will also look at specific signs in the blood and tumor to see if they can help predict how well the treatment is working. This could help better understand how dostarlimab contributes to the response of the disease to treatment.

The primary purpose of this study is to evaluate the efficacy of perioperative dostarlimab compared with standard of care (SOC) in participants with untreated T4N0 or Stage III (resectable), defective mismatch repair/ microsatellite instability high (dMMR/MSI-H) colon cancer.