Preoperative Short-course Radiation Followed by Envafolimab Plus CAPEOX for MSS Locally Advanced Rectal Adenocarcinoma

This study is testing whether giving a short course of radiation followed by immunotherapy (envafolimab) and chemotherapy (CAPEOX) before surgery improves outcomes for people with locally advanced rectal cancer that is classified as microsatellite stable (MSS) — a subtype that typically does not respond well to immunotherapy alone. **You may be eligible if...** - You are 18 or older with locally advanced rectal cancer (tumor within 12 cm of the anal opening) - Your cancer has been confirmed as rectal adenocarcinoma by biopsy - Your cancer is MSS or pMMR (a test result showing the cancer is less likely to respond to standard immunotherapy) - You have not previously received any cancer treatment - Your blood counts and organ function meet the study requirements **You may NOT be eligible if...** - Your cancer has spread to other parts of the body (Stage IV) - Your cancer is MSI-H or dMMR (a different molecular subtype) - You have had prior cancer treatment - You have allergies to oxaliplatin, capecitabine, or PD-L1 antibody drugs - You have intestinal obstruction, perforation, or bleeding requiring emergency surgery Talk to your doctor to see if this trial is right for you.