To explore the significance of lymph node metastasis in surgical treatments of nonfunctional pancreatic neuroendocrine tumors (pNET).

Clinical data of 322 patients with nonfunctional pNET undergoing surgery in Fudan University Shanghai Cancer Center from January 2010 to December 2018 were retrospectively analyzed. Among them, 131 patients were male and 191 female, aged 16-77 years with a median age of 52 years. The informed consents of all patients were obtained and the local ethical committee approval was received. The clinicopathological factors related to lymph node metastasis were analyzed by Chi-square test. The potential factors were subjected to multivariate Logistic regression analysis. All patients were divided into the lymph node metastasis and non-lymph node metastasis groups. The effect of lymph node metastasis on patients' overall survival (OS) was analyzed. Survival analysis was performed with Kaplan-Meier method and Log-rank test.

The incidence of lymph node metastasis was 23.3%(75/322), including 66 cases of R0 resection and 9 cases of R1 resection. Univariate analysis showed that tumor diameter >3 cm and pathological grade G3 were significantly correlated with lymph node metastasis in nonfuctional pNET patients (χ2=5.361, 5.554; P<0.05). Multivariate Logistic regression analysis demonstrated that tumor diameter >3 cm and pathological grade G3 were the independent risk factors for lymph node metastasis in nonfunctional pNET patients (OR=4.196, 4.673; 95%CI: 1.140-15.450, 1.377-15.864; P<0.05). The postoperative follow-up was ranged from 2.2 to 152.8 months with a median follow-up time of 44.1 months. The median OS in the lymph node metastasis and non-lymph node metastasis groups was 31.5 and 47.8 months, respectively, and significant difference was observed in OS between two groups (χ2=6.093, P<0.05).

Tumor diameter >3 cm and low differentiation are independent risk factors for lymph node metastasis in nonfunctional pNET patients. The prognosis of these patients is poor. Radical resection including regional lymph node dissection is recommended.