Toripalimab Plus Celecoxib for dMMR/MSI-H Locally Advanced Colorectal Cancer

This study is testing whether combining an immunotherapy drug (toripalimab) with an anti-inflammatory drug (celecoxib) before surgery can shrink locally advanced colorectal cancer that has a specific genetic feature (called dMMR or MSI-H) making it more likely to respond to immunotherapy. **You may be eligible if...** - You are 18 or older - You have been diagnosed with colorectal cancer confirmed by biopsy - Your cancer is locally advanced (has grown into nearby tissue or lymph nodes) but has NOT spread to distant organs - Your tumor has the dMMR or MSI-H genetic marker - You have not received any prior cancer treatment (surgery, chemo, radiation) for this cancer - Your organs (heart, liver, kidneys) are functioning well enough for treatment **You may NOT be eligible if...** - Your cancer has spread to other parts of the body - You have a complete bowel obstruction, active bleeding, or perforation needing emergency surgery - You have had prior immunotherapy (anti-PD-1/PD-L1 or anti-CTLA-4) - You have an active autoimmune disease or serious heart condition - You have untreated HIV or active hepatitis Talk to your doctor to see if this trial is right for you.