Importance of Lymph Node Involvement in Pancreatic Neuroendocrine Tumors: Impact on Survival and Implications for Surgical Resection

Background Conflicting data exist on predictors of nodal metastases and their impact on survival in patients with pancreatic neuroendocrine tumors (PNETs). We aim to identify factors associated with lymph node involvement and evaluate the effect of nodal metastases on survival. Methods All patients undergoing surgery for PNETs in the Surveillance, Epidemiology, and End Results (SEER) tumor registry from 1988 to 2010 were included. Predictors of lymph node involvement and disease-specific survival (DSS) were evaluated using logistic regression and Cox regression, respectively. Results Patients (1,915) underwent surgery for a PNET (62 % nonfunctional). Nodal positivity was associated with increasing tumor size (p<0.001) and grade (p<0.001). Unadjusted DSS at 5 years was 81 % for N0, 74 % for Nx, and 69 % for N1, respectively, (p<0.001). After adjustment for tumor size and grade, DSS was significantly decreased in N1 patients (HR 1.57; 95 % CI 1.23-1.95). For patients who had at least one node examined and had low-grade PNETs <1 cm, no nodal metastases were found. Conclusions High tumor grade and increasing size predict nodal metastases in patients with PNETs. N1 status is independently associated with decreased DSS. Low-grade tumors <1 cm may be observed or enucleated.