A Phase II Trial of Long-Course Chemoradiotherapy or Short-Course Radiotherapy Combined With CAPOX, PD-1 Antibody, and COX-2 Inhibitor for Microsatellite Stable Locally Advanced Rectal Cancer

What this Trial Is About

Researchers are evaluating treatments for patients with locally advanced rectal cancer (LARC) who have tumors close to the anus and no distant spread. This phase II trial compares two groups receiving neoadjuvant therapy before surgery to see which leads to a higher complete response rate, including both pathological and clinical complete responses. The trial also studies side effects, anal preservation, and survival over three years among others. One group receives long-course chemoradiotherapy (50 Gy in 25 fractions) followed by three cycles of CAPOX chemotherapy (capecitabine and oxaliplatin). The other group receives short-course radiotherapy (25 Gy in 5 fractions) followed by four cycles of CAPOX combined with a PD-1 antibody called serplulimab. During chemotherapy, both groups take the COX-2 inhibitor celecoxib orally twice daily until the end of the neoadjuvant treatment. Surgery is planned after total neoadjuvant therapy, but patients who achieve clinical complete response may have a watch-and-wait option instead. Participants will undergo assessments including response evaluation one month after surgery or the watch-and-wait decision. Researchers will monitor for severe side effects from treatment, anal preservation rates, and disease-free survival for up to three years. Surgical complications will be tracked for three months post-surgery. Participants are expected to comply with the study protocol and provide informed consent, with study care and monitoring occurring from enrollment through the follow-up period until August 2028.

Long-course Chemoradiotherapy or Short-course Radiotherapy Combined With CAPOX, PD-1antibody, and COX-2 Inhibitor for MSS Locally Advanced Rectal Cancer (SERRAC)