This phase II, multi-center, open-label, 3-arm, randomized trial aims to recruit patients aged 18-75 years, diagnosed histologically as rectal adenocarcinoma, without metastasis (by CT), staged II/III (by MRI, T4b excluded), with distal margin within 10cm to anal verge. All patients should have no history of immune diseases, nor history of immunotherapy or radiotherapy. Sample size was thoroughly calculated to be 186. Eligible participants will be randomly assigned to Experiment Arm 1 (50.4Gy radiation, capecitabine, and anti-PD1 starting at Day 8 of radiation), Experiment Arm 2 (50.4Gy radiation, capecitabine, and anti-PD1 starting 2 weeks after completion of radiation), and Control Arm (50.4Gy radiation, capecitabine) in a 1:1:1 ratio. Randomization is stratified by different centers, with a block size of 6. For both experiment arms, Tislelizumab (anti-PD1) is scheduled to be administered at 200mg each time for 3 times, with 3-week intervals. The primary endpoint is pCR rate, and secondary endpoints include sphincter-preserving rate, adverse event rates, and DFS and OS rate at 2, 3 and 5 years post-operation. Data will be analyzed with an intention-to-treat approach.
This is a phase II/III, multi-center, open-label, 3-arm, randomized controlled trial assessing the efficacy and safety of neoadjuvant long-course chemoradiation combined with Tislelizumab (PD-1 inhibitor) and subsequent TME surgery, by comparing assorted endpoints between two experiment groups (Experiment group 1: chemoradiation+concurrent PD-1 inhibitor; Experiment group 2: chemoradiation+sequential PD-1 inhibitor) with a control group (chemoradiation only).