mFOLFOX6 + Bevacizumab + PD-1 Monoclonal Antibody Vs. mFOLFOX6 in Locally Advanced pMMR/MSS CRC

Participants in the experimental group will receive the neoadjuvant therapy regimen of mFOLFOX6 + Bevacizumab + PD-1 monoclonal antibody. And the first five doses received the neoadjuvant therapy regimen of mFOLFOX6 (intravenous oxaliplatin 85 mg/m2, leucovorin 400 mg/m2, 5-fluorouracil 400 mg/m2, and 5-fluorouracil 2400 mg/m2 continuous pumping for 48 hours) combined with sintilimab (200 mg, intravenous) and Bevacizumab (5 mg/kg, intravenous), and the sixth dose received the same regimen of mFOLFOX6 and PD-1 monoclonal antibody but not plus bevacizumab, in order to allow sufficient withdrawal time of Bevacizumab for surgery.

Participants in the control group will receive the neoadjuvant therapy regimen of mFOLFOX6 (intravenous oxaliplatin 85 mg/m2, leucovorin 400 mg/m2, 5-fluorouracil 400 mg/m2, and 5-fluorouracil 2400 mg/m2 continuous pumping for 48 hours) alone.