The Efficacy of Watch and Wait Strategy or Surgery After Neoadjuvant Immunotherapy for Locally Advanced Colorectal Cancer With dMMR/MSI-H Guided by MRD Dynamic Monitoring: A Single-center, Open-label, Prospective, Phase II Clinical Trial.

"Neoadjuvant immunotherapy phase :~1. Pharmaceuticals: Tireilizumab: 200mg, intravenous infusion, Q3W, at least 4 cycles, the number of specific neoadjuvant immunotherapy cycles was determined according to the results of MRD dynamic monitoring.~2. MRD dynamic monitoring time node: dynamic monitoring at the initial diagnosis and after the fourth cycle of neoadjuvant immunotherapy. Blood monitoring points were 1-2 weeks after immunotherapy. If the two consecutive MRDs were negative, the watch and wait strategy was adopted. If the MRD was still positive after 8 cycles of neoadjuvant immunotherapy, surgical treatment was performed."