224 Background: Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are a diverse group of malignancies affecting over 65,000 patients in the United States. GEP-NETs are currently classified as lymph node positive (N1) or negative (N0). The prognostic utility of the extent of lymph node involvement remains unknown. In this study, we used a population-based registry to investigate the relationship between lymph node ratio (LNR) and survival in patients with GEP-NETs. Methods: We used the Surveillance, Epidemiology, and End Results (SEER) data registry to identify patients with histologically confirmed, surgically resected NETs with lymph node involvement diagnosed between 1988 and 2011. Patients were divided into three groups based on the ratio of positive lymph nodes to total lymph nodes examined (LNR): ²0.20, >0.2-0.5, and >0.5. Kaplan-Meier, log-rank analysis, and Cox models were used to compare NET cancer-specific survival according to LNR category. Results: We identified 8,113 patients with GEP-NETs. Primary sites included small intestine (N=3,651), colon (N= 2,042), pancreas (N=1,070), appendix (N= 683), stomach (N=389), and rectum (N=278). Patients were 49% female, 76% white, and 12% black. Ten-year NET-specific survival rates were significantly different among patients in the three LNR groups and LN negative controls (p<.0001). Survival was worse in patients with LNRs of >0.2-0.5 (Hazard Ratio (HR) 1.338, p=.0002), and >0.5 (HR 1.692, p<.0001) compared to LN-negative controls. Higher LNR was correlated with worse survival. Conclusions: The degree of lymph node involvement is a prognostic factor across the most common primary sites of GEP-NETs. This information may be used clinically and in stratifying patients for clinical trials. Results across multiple sites may also be generalizable to GEP-NETs from rare primary locations that are difficult to study. [Table: see text]
Pattern and Clinical Predictors of Lymph Node Involvement in Nonfunctioning Pancreatic Neuroendocrine Tumors (NF-PanNETs)