Neoadjuvant Immunotherapy for T4 dMMR Colon Cancer

This trial is testing whether giving immunotherapy before surgery (neoadjuvant immunotherapy) can help treat a specific type of locally advanced colon cancer. The cancer targeted here is dMMR (mismatch repair deficient) colon cancer — a subtype that is known to respond well to immunotherapy because of how its DNA repair works. The goal is to shrink or even eliminate the tumor before surgery, potentially making it easier to remove and improving long-term outcomes. **You may be eligible if...** - You are 18 to 75 years old - You have colon cancer confirmed by biopsy that is dMMR (a specific genetic feature confirmed by a lab test) - Your tumor is located in the right-side or middle of the colon (cecum, ascending, transverse, or sigmoid) - Your cancer has grown into surrounding structures (T4 stage) and cannot be fully removed without difficulty - You have not had any previous chemotherapy or surgery for this cancer - Your organs are healthy enough to tolerate treatment **You may NOT be eligible if...** - You have another active cancer (diagnosed in the past 5 years, with some exceptions) - You have a bowel obstruction, perforation, or serious bleeding requiring emergency surgery - You are pregnant or breastfeeding - You have a history of severe mental illness or autoimmune disease requiring immune-suppressing treatment Talk to your doctor to see if this trial is right for you.