Immunotherapy (Toripalimab) for Reducing Recurrence Risk After Surgery for Mismatch Repair Deficient Stage IIB, IIC, or III Colon Cancer

This study is testing whether an immunotherapy drug called toripalimab (a PD-1 inhibitor that helps the immune system fight cancer) given after surgery can prevent colon cancer from coming back in patients with a specific type of cancer called dMMR (mismatch repair deficient) colon cancer, which tends to respond particularly well to immunotherapy. **You may be eligible if...** - You have had surgery to remove stage IIB, IIC, or III colon cancer within the past 4 to 12 weeks - Your cancer has been confirmed as mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H) by testing - The surgery completely removed the cancer (R0 resection) - Your blood counts and organ function meet study requirements **You may NOT be eligible if...** - Your colon cancer is mismatch repair proficient (pMMR) or not MSI-H - You have had prior immunotherapy - You have active autoimmune disease - You are pregnant or breastfeeding - Your cancer has already spread to distant organs Talk to your doctor to see if this trial is right for you.