Neoadjuvant Therapy With Tislelizumab for dMMR/MSI-H Stage II-III Colorectal Cancer

This study is testing tislelizumab, an immunotherapy drug, given before surgery for stage II or III colorectal cancer that has a specific genetic feature called dMMR or MSI-H. This type of colorectal cancer responds unusually well to immunotherapy, and researchers want to see if giving it before surgery can shrink or even eliminate the tumor. **You may be eligible if:** - You are 18 or older with good general health (ECOG performance status 0–2) - You have been diagnosed with stage II or III colorectal cancer confirmed by biopsy - Your tumor has been tested and found to be dMMR or MSI-H (a specific genetic marker) - You have signed an informed consent form **You may NOT be eligible if:** - You have other serious medical conditions that make surgery unsafe - You have active autoimmune disease, inflammatory bowel disease, chronic infections, or a history of organ transplant - You are on long-term immune-suppressing medications - You have had a severe allergic reaction to tislelizumab or similar drugs (PD-1/PD-L1 inhibitors) - You have severe lung scarring (pulmonary fibrosis) Talk to your doctor to see if this trial is right for you.