Maintenance Tislelizumab + Capecitabine to Treat Metastatic Colorectal Cancer

This study is testing whether adding the immunotherapy drug tislelizumab plus the oral chemotherapy drug capecitabine as maintenance treatment can prevent colorectal cancer from coming back after surgery and chemotherapy achieved no visible remaining disease. **You may be eligible if...** - You are between 20 and 79 years old - You have colorectal cancer that spread (metastatic) and underwent surgery, achieving no evidence of disease - Your surgery removed all visible tumors (CC0 resection if peritoneal spread was present) - You have not received any prior chemotherapy - You had no more than 3 sites of metastatic spread **You may NOT be eligible if...** - You had prior chemotherapy for colorectal cancer - You have active autoimmune disease - You have uncontrolled serious medical conditions - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.