Significance of lymph node metastasis in pancreatic neuroendocrine tumor

Purpose Pancreatic neuroendocrine tumor (PNET) is relatively rare and has a generally better prognosis than does pancreatic cancer. However, as its prognosis in patients with lymph node metastasis (LNM) is unclear, lymph node dissection for PNET is controversial. Our study aimed to clarify the significance of LNM in PNET. Methods We retrospectively examined 83 PNET patients who underwent pancreatic resections with lymph node dissection at Kumamoto University Hospital, Saiseikai Kumamoto Hospital, and Kumamoto Regional Medical Center from April 2001 to December 2014. Their clinicopathological parameters were analyzed by the absence or presence of LNM, and with regard to the disease-free survival (DFS) and overall survival (OS). A predictive score of LNM was also made using the age, tumor size, primary tumor location, and tumor function. Results Although the 5-year OS was 74.8% for LN+ and 94.6% for LNM-(P=0.002), LNM was not an independent risk factor for the OS in a multivariate analysis. However, tumors larger than 1.8 cm were found to be an independent prognostic factor, and the cut-off value for the predictive score was 1.69. Conclusions Although LNM was not an independent prognostic factor, lymph node dissection is recommended for patients whose predictive score is larger than 1.69.