The safety and efficacy of immune checkpoint inhibitor in combination with FOLFOX as neoadjuvant/adjuvant therapy in patients with locally advanced colon cancer.

e15621 Background: The recurrence rate of locally advanced colon cancer (T3-4 or N+, M0) after surgery is significantly high. Emerging data indicate that the combination of immunotherapy and chemotherapy demonstrates synergistic effects in other solid tumors. Consequently, a combination of immunotherapy and chemotherapy holds the potential to benefit patients with MSS and pMMR colon cancer. We have designed a prospective trial to investigate whether the immune checkpoint inhibitor (ICI) in combination with chemotherapy represents a safe and beneficial treatment approach for locally advanced colon cancer. Methods: Inclusive Criteria: Patients with locally advanced colon cancer (T3-4 or N+, M0) confirmed through pathological biopsy, with confirmed indications for neoadjuvant/adjuvant chemotherapy by the multidisciplinary team. Patients must be eligible for surgery, and a measurable mass must be identified according to RECIST version 1.1. All individuals aged over 18 years, with an estimated life expectancy of over one year and an ECOG score within 0-1, are eligible. The neoadjuvant chemoimmunotherapy group (NACI) includes mFOLFOX 6 (Q2W) and the anti-PD-1 monoclonal antibody (Toripalimab) (3mg/kg, Q2W), while the neoadjuvant chemotherapy group (NAC) receives only mFOLFOX 6 for neoadjuvant/adjuvant therapy (a total of 12 cycles, 6 cycles pre-surgery and 6 cycles post-surgery). The primary endpoint is the pathological complete response (pCR) rate. Results: From 2019 to 2022, a total of 22 patients were enrolled in the study, with 13 in the NACI group and 9 in the NAC group. The research findings indicate that in the NACI group, over 30% (4/13) of patients achieved a pathological complete response (pCR), whereas none of the patients in the NAC group reached pCR (0/9). Among the pCR patients, one was identified as MSI-H/dMMR, two as MSS/pMMR, and one had an unknown status. Tumor regression grade (TRG) levels also revealed that all patients in the NACI group were below grade 2, significantly outperforming the NAC group (P < 0.05), with statistically significant differences. However, no significant differences were observed between the NAC and NACI groups in terms of CT regression percentage, R0 resection, vascular cancer emboli, and the level of neural invasion. Adverse reactions did not show significant differences between the two groups. Conclusions: The combination of immunotherapy and chemotherapy exhibits a synergistic effect in treating locally advanced colorectal cancer. Tolerable adverse reactions suggest that neoadjuvant chemoimmunotherapy could potentially serve as a novel therapeutic option. Clinical trial information: NCT03985891 .