[Impact of perineural invasion upon chemotherapy duration and survival benefit in stageⅢ colon cancer].

Objective: To investigate the prognostic impact of perineural invasion in patients with stageⅢ colon cancer and to clarify its guidance value for the duration of postoperative adjuvant chemotherapy. Methods: This study employed a retrospective cohort study method. It analyzed 426 patients with stageⅢ colon cancer who underwent radical surgery at Sun Yat-sen University Cancer Center and Longyan First Affiliated Hospital of Fujian Medical University, between April 2008 and June 2020. Inclusion criteria: patients received at least 3 months of adjuvant CapeOX therapy post-surgery, had complete pathological data, and were followed up for at least 12 months after the last chemotherapy. Among these patients, 231 were male, the median age was 59 (50~67) years, and 263 tumors were located in the right-sided colon. Postoperative pathology indicated that 107 cases (25.12%) had neural invasion, and 131 patients (30.75%) had vascular tumor thrombus. All patients received at least 4 cycles of postoperative CapeOX adjuvant chemotherapy, with 193 patients receiving 8 cycles and 233 patients receiving 4 to 7 cycles of adjuvant chemotherapy. The study analyzed the impact of neural invasion status and the duration of adjuvant chemotherapy on disease-free survival (DFS). Furthermore, within subgroups stratified by different risk levels (referencing the criteria proposed by the IDEA study: high risk: T4, N2 or T4N2; low risk: T3N1) and different neural invasion statuses, the impact of the duration of adjuvant chemotherapy on prognosis was analyzed. Results: The median follow-up time for the entire cohort was 94.00 months (55.27-128.80 months). Multivariate Cox analysis indicated that pathological T stage T4 (HR = 2.457, 95%CI: 1.499-4.029, P<0.001) and postoperative pathological confirmation of perineural invasion (HR = 2.465, 95% CI: 1.519-4.000, P<0.001) were independent adverse prognostic factors for 5-year DFS. In the perineural invasion-positive group, the 5-year DFS for patients who received 8 cycles of postoperative adjuvant CapeOX chemotherapy was 86.90%, compared to 58.22% for those who received 4-7 cycles, with statistically significant differences (both P<0.05). In the perineural invasion-negative group, the 5-year DFS for patients who received 8 cycles was 88.66%, compared to 90.99% for those who received 4-7 cycles, with no statistically significant differences (P=0.929). Among IDEA high-risk patients with perineural invasion, the 5-year DFS was 91.81% for those who received 8 cycles versus 50.66% for those who received 4-7 cycles, showing a statistically significant difference (P=0.003). In IDEA high-risk patients without perineural invasion, the 5-year DFS for those who received 8 cycles was 82.28% compared to 87.32% for those who received 4-7 cycles, with no statistically significant difference (P=0.806). In the IDEA low-risk patients, no differences were observed in the 5-year DFS between patients receiving 8 cycles and those receiving 4-7 cycles of adjuvant CapeOX chemotherapy in both perineural invasion-positive and negative subgroups (both P>0.05). Conclusion: Perineural invasion serves as a significant prognostic factor for 5-year DFS in stage Ⅲ colon cancer patients who have undergone radical surgery and postoperative adjuvant chemotherapy. It can also be considered an important reference factor in deciding the duration of postoperative adjuvant chemotherapy.