Serplulimab Combined With CAPEOX + Celecoxib as Neoadjuvant Treatment for Locally Advanced Rectal Cancer

This trial tests a combination of treatments before surgery (called neoadjuvant therapy) for people with locally advanced rectal cancer. The combination includes an immunotherapy drug called serplulimab, two chemotherapy drugs (capecitabine and oxaliplatin, known as CAPEOX), and celecoxib (an anti-inflammatory medicine). The goal is to shrink the tumour before surgery and improve long-term outcomes. **You may be eligible if...** - You are 18 to 75 years old - You have been diagnosed with rectal cancer confirmed by biopsy - Your cancer has not spread to other parts of the body (non-metastatic) - You have not had any previous cancer treatment for this rectal cancer - Your tumour is within 10 cm of the anal opening - You are in good general health **You may NOT be eligible if...** - Your rectal cancer has come back after previous treatment, or you have had pelvic radiation before - You have inflammatory bowel disease (such as Crohn's or ulcerative colitis) - You have HIV, or both hepatitis B and C infections - You have had an organ or bone marrow transplant - You have a significant heart condition (such as a recent heart attack, severe heart failure, or poorly controlled blood pressure) - You have had major surgery in the past 4 weeks - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.