This is an open, prospective, multi-center, single-arm phase II clinical study assessing the efficacy and safety of neoadjuvant chemoradiotherapy combined with PD-1 inhibitor and thymalfasin in patients with pMMR/MSS locally advanced middle and low rectal cancer.

This study is an open, prospective, multi-center, single-arm phase II clinical study. In this study, patients with pMMR/MSS locally advanced middle and low rectal cancer were selected as the subjects and treated with neoadjuvant treatment protocol of long-course concurrent chemoradiotherapy combined with PD-1 monoclonal antibody and thymalfasin. The primary endpoint of the study was complete response (CR) rate. The secondary end points included treatment-related adverse events (TRAEs) rate, 30-day incidence of postoperative complications, objective response rate (ORR), 3-year disease-free survival (DFS) rate, Neoadjuvant rectal cancer (NAR) score, R0 resection rate, and anal preservation rate.