Total Neoadjuvant Therapy Combined With Tislelizumab for Local Advanced of Middle and Low Rectal Cancer

This study is a prospective, randomized, open, controlled, multi-center phase II clinical trial, which included patients with locally advanced low rectal cancer as the research object, and evaluated the application of long-term concurrent chemoradiotherapy combined with tislelizumab versus long-term synchronous Efficacy and safety of chemotherapy and radiotherapy as neoadjuvant therapy for patients with locally advanced rectal cancer. The main endpoints of the study were clinical complete response (cCR) (including imaging and endoscopic complete response) and pathological complete response (pathological complete response, pCR). Secondary study endpoints are primary pathological response rate (MPR), objective response rate (ORR), disease-free survival (DFS), overall survival (OS), organ preservation rate (OPR), rectal cancer neoadjuvant therapy score (NAR ), quality of life score (QoL), safety and tolerability. They will be randomly divided into an experimental group (tislelizumab combined with long-term concurrent chemoradiotherapy) and a control group (long-term concurrent chemoradiotherapy) at a ratio of 2:1. Random stratification factors: 1. TNM stage (II/III); 2. Distance from the tumor to the anal verge (≥5cm, \<5cm).