Safety and Efficacy of PD-1 ± mFOLFOX6 Neoadjuvant Therapy in Local Advanced sMPCC

At present, radical resection ± preoperative neoadjuvant chemotherapy for colorectal cancer is still the standard comprehensive treatment. In recent years, immunotherapy of PD-1 monoclonal antibody has a significant effect in the second-line/first-line treatment of dMMR/MSI-H advanced colorectal cancer and the neoadjuvant treatment of early colorectal cancer. Synchronous multiple primary colorectal cancer (sMPCC) is a relatively rare type of colorectal cancer (CRC) that refers to the simultaneous occurrence of 2 or more independent primary malignancies in the colon or rectum. The recent large-scale, single-center retrospective study of the investigator showed that compared with single primary colorectal cancer (SPCRC)patients, the incidence of dMMR/MSI-H was significantly higher in sMPCC patients. Besides, a certain proportion of sMPCC patients could both have MSI and MSS tumors at the same time. There is no standard regimen for this patients so far. This study intends to treat the MSI-H/MSS (dMMR/pMMR) mixed sMPCC patients with combination of mFOLFOX6+PD-1 monoclonal antibody neoadjuvant therapy, and treat the all-MSI-H (dMMR) sMPCC patients with single-drug PD-1 monoclonal antibody neoadjuvant therapy. Given the current gaps in the guideline, the investigator intends to take the lead in carrying out this open, multi-center, prospective clinical phase II study. This study might provide a clinical evidence for individual treatment of sMPCC patients, in preserving the functions and organs to the greatest extent.