Neoadjuvant Chemotherapy With PD-1 Inhibitors Combined With SIB-IMRT in the Treatment of Locally Advanced Rectal Cancer

This trial tests whether combining an immunotherapy drug (a PD-1 inhibitor) with standard chemotherapy before surgery, along with a specialized radiation technique (SIB-IMRT), improves outcomes for people with locally advanced rectal cancer. **You may be eligible if...** - You are between 18 and 70 years old - You have confirmed rectal adenocarcinoma (a specific type of rectal cancer) that is locally advanced (T3–T4 or lymph node-positive) - You have not started any treatment yet - You are doing well enough in daily activities (ECOG 0–1) - Your blood counts and organ function meet required levels **You may NOT be eligible if...** - You have had other cancers in the last 5 years - You have received prior PD-1 or checkpoint immunotherapy - You have an active autoimmune disease or active infection - You are pregnant or breastfeeding - You have a history of heart attack, stroke, or severe heart failure Talk to your doctor to see if this trial is right for you.