A Randomized Phase II Study of Long-term Chemoradiotherapy or Short-term Radiotherapy Combined With CAPOX, PD-1 Monoclonal Antibody and COX-2 Inhibitors in MSS Type Locally Advanced Rectal Cancer
This randomized phase II trial evaluates the efficacy of long-course chemoradiotherapy (50Gy/25Fx + capecitabine) versus short-course radiotherapy (25Gy/5Fx) combined with CAPOX（Capecitabine and Oxaliplatin）, PD-1 inhibitor (serplulimab), and COX-2 inhibitor (celecoxib) in MSS（MicroSatellite Stable） locally advanced rectal cancer, with primary endpoint of complete response rate (pCR+cCR)（Complete Remission） and secondary endpoints including anal preservation rate and 3-year survival outcomes, aiming to elucidate the immunomodulatory effects of triple therapy on tumor microenvironment.
• Age 18-75 years, regardless of gender.
• Pathologically confirmed rectal adenocarcinoma.
• Tumor located ≤10 cm from the anal verge.
• Baseline stage T3-4 and/or N+ (locally advanced disease).
• No evidence of distant metastasis.
• Microsatellite stability (MSS) or proficient mismatch repair (pMMR).
• Karnofsky Performance Status (KPS) ≥70.
• No prior chemotherapy or any other anticancer therapy before enrollment.
• No prior immunotherapy.
• Able to comply with study protocol requirements throughout the study period.
• Signed written informed consent obtained prior to study participation.