Prognostic value of lymph node positivity and number of lymph nodes required for accurate staging of pancreatic neuroendocrine tumors.

Abstract

e15736 Background: The prognostic role of the number of positive lymph nodes (PLNs), as well as the minimum number of lymph nodes needed to accurately stage patients with pancreatic neuroendocrine tumors (pNETs), remain controversial. The aim of this study was to assess the effect of the number of PLNs on prognosis in pNETs and to determine the ideal number of examined lymph nodes (ELNs) for accurate staging of pNETs. Methods: The SEER database was reviewed from 2004 to 2014 for pts with surgically resected, pathologically confirmed pNETs. Pts with missing data for pathological stage, tumor size, ELNs or PLNs were excluded. Kaplan-Meier survival analysis was used to evaluate the association between lymph node involvement and disease-specific survival (DSS). The optimal number of ELNs was identified using the log odds of positive lymph nodes (LODDS). A large single institutional cohort with 203 patients was used for validation. Results: Of the 1,813 patients included, 686 (37.8%) had lymph node-positive disease. Patients with lymph node-positive disease had a significantly worse DSS than those with lymph node-negative disease (Log-rank P < 0.001). Patients with 4 or more positive lymph nodes had a worse DSS compared with those with 1 to 3 positive lymph nodes (Log-rank P < 0.001). In order to capture 95% of pNETs with PLNs at the time of surgery, 12 lymph nodes need to be examined (LODDS: -2.344). Findings were reproducible with the validation cohort. Conclusions: The number of PLNs leads to better prognostic discrimination of lymph node-positive patients with pNETs. The current staging systems may include an N-stage that distinguishes lymph node-positive disease into N1 (1 to 3 PLNs) and N2 (4 or more PLNs) categories. The minimum number of ELNs for accurate staging of pNETs is 12. [Table: see text]