Safety and Efficacy of PD-1 Monoclonal Antibody With or Without mFOLFOX6 Neoadjuvant Therapy in Patients With Local Advanced Deficient Mismatch Repair/Microsatellite Instability-high Synchronous Multiple Primary Colorectal Cancer (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.
• Histological confirmation of simultaneous multiple primary colorectal cancer (sMPCC);
• Tumor biopsy immunohistochemistry of at least one tumor lesion identified dMMR, including the expression loss of one or more of the four proteins MSH1, MSH2, MSH6 and PMS2; or at least one tumor lesion identified MSI-H by polymerase chain reaction or next-generation sequencing technique;
• Clinical staging T3-4NxM0, with or without positive MRF, with or without positive EMVI;
• Staging method: all patients undergo chest,abdominal and pelvic enhanced CT, rectal palpation, high resolution MRI examination，positive perienteric lymph node(LN): short diameter ≥10mm LN or LN with typical metastatic shape and MRI character, clinical data should be re-evaluated and judged by center evaluation group when there are contradictory stagings，distant metastasis were excluded by chest and abdominal enhanced CT and pelvic enhanced MRI;
• No intestinal obstruction symptom，or obstruction relieved after proximal colostomy;
• No colorectal surgery history;
• No chemotherapy or radiotherapy history;
• No biopharmaceutical treatment history(such as monoclonal antibody), immunotherapy(such as anti PD-1antibody, anti PD-L1 antibody, anti PD-L2 antibody or anti CTLA-4), or other research drug treatment;
• No endocrinotherapy history restriction;
⁃ informed consent assigned.