Study on the Efficacy and Safety of Neoadjuvant Radiotherapy Combined With Toripalimab, Liposomal Irinotecan, and Capecitabine in the Treatment of pMMR Locally Advanced Rectal Adenocarcinoma With Low Rectal Involvement

This study is testing a combination of radiation therapy plus immunotherapy (toripalimab), a new chemotherapy drug (liposomal irinotecan), and capecitabine (an oral chemo pill) before surgery in people with locally advanced rectal cancer. **You may be eligible if...** - You are between 18 and 75 years old - You have locally advanced rectal cancer confirmed by biopsy — specifically a type called pMMR (proficient mismatch repair) - Your tumor is in the lower part of the rectum (within 10 cm of the anal opening) - You have high-risk features such as lymph node involvement or the tumor being close to surrounding tissue - Your blood counts and organ function are in acceptable range **You may NOT be eligible if...** - Your tumor is MSI-high or dMMR (a different genetic type that responds differently to immunotherapy) - You have distant metastasis (cancer spread to other organs) - You have active autoimmune disease or are on immunosuppressive therapy Talk to your doctor to see if this trial is right for you.