Phase II RCT of LCRT vs SCRT + CAPOX/PD-1i/COX-2i in MSS Locally Advanced Rectal Cancer

This study is comparing two radiation-based treatment approaches for locally advanced rectal cancer that does not have a specific genetic marker (MSS type). One approach uses long-course chemoradiation, while the other uses short-course radiation followed by chemotherapy plus immunotherapy and a COX-2 inhibitor. **You may be eligible if...** - You are between 18 and 75 years old - You have confirmed rectal cancer located within 10 cm of the anal opening - Your cancer has spread to the wall or nearby lymph nodes but not to distant organs - Your cancer is the microsatellite stable (MSS) type - You have not had any prior chemotherapy or anticancer treatment - Your overall physical function is adequate (Karnofsky score 70 or above) **You may NOT be eligible if...** - You are pregnant or breastfeeding - You have had another cancer in the past 5 years (except cured skin cancer or cervical in situ) - You have serious heart disease, autoimmune disease, or active uncontrolled infection - You are on long-term steroids or immunosuppressant medications - You have a known deficiency in processing fluorouracil-type drugs (DPD deficiency) Talk to your doctor to see if this trial is right for you.