Objectives:~To clarify the efficacy and safety of combined therapy for locally advanced rectal cancer (LARC) patients and verify the efficacy and safety of neoadjuvant immunotherapy for dMMR/MSI-H LARC patients.~To clarify the effect of nCRT on TIME for rectal cancer, and the further effect of adding Immunotherapy.~To verify the feasibility of predicting the efficacy of combined therapy by the infiltration level of CD8+ PD1+ TILs in tumor tissue before treatment in pMMR/MSS LARC patients and explore the comprehensive prediction index of the efficacy of combined therapy for LARC patients.~To clarify the potential mechanism of immune response or immune escape to neoadjuvant immunotherapy for LARC patients.
This is an open-label, prospective phase II clinical trial to evaluate the therapeutic and prognostic implications of tumor immune microenvironment in the neoadjuvant immunotherapy combined with chemoradiotherapy for patients with rectal cancer. A total of 100 patients will be enrolled in this trial. The primary end point is the rate of pathological complete response (pCR). The long-term prognosis and adverse effects will also be evaluated and analyzed.