Regional Metastatic Behavior of Nonfunctional Pancreatic Neuroendocrine Tumors: Impact of Lymph Node Positivity on Survival

Objectives Literature addressing the significance of lymph node positivity in the management of nonfunctional pancreatic neuroendocrine tumors (PNETs) is conflicting. Methods The National Cancer Data Base was queried for patients who underwent surgical resection of nonfunctional PNETs between 1998 and 2011. Clinical data and overall survival were analyzed using χ² and Cox proportional hazards regression. Multiple imputation was used as a comparative analysis because of the high number of patients missing data on tumor grade. Results Two thousand seven hundred thirty-five patients were identified. The overall incidence of lymph node metastasis was 51%. In the subset of patients with grade 1 tumors less than 1 cm, 24% had positive lymph nodes. Overall median survival for patients with negative lymph nodes was 11 years compared with 8 years for lymph node-positive patients (P < 0.001). On multivariate survival analysis, tumor grade, distant metastases, regional lymph node involvement, positive surgical margins, male sex, and older age were predictive of decreased overall survival. Conclusions Lymph node positivity was associated with decreased overall survival. The incidence of lymph node involvement in resected low-grade tumors less than 1 cm is higher than previously reported. Patients selected for resection of PNETs should be offered lymphadenectomy for staging.