326 Prognostic Significance of the Extent of Lymph Node Metastases in Small Intestinal Neuroendocrine Tumors

Abstract

Introduction: In patients with small intestinal neuroendocrine tumors (SI-NETs), current NET staging guidelines differentiate only between the presence (N1) and absence (N0) of lymph node (LN) metastases. However, the prognostic significance of the extent of LN involvement remains unknown. In this study, we used data from a national populationbased cancer registry to examine whether involvement of a higher number of LNs is associated with worse survival. Methods: We used the Surveillance, Epidemiology and End Results (SEER) database to identify patients with histologically confirmed, surgically resected SINETS diagnosed between 1988 and 2010. Because the number of positive LNs is confounded by the total number of LNs removed, patients were classified into three groups by the lymph node ratio (number of positive lymph nodes/number of total lymph nodes examined, LNR): ≤0.15, 0.16-0.5, and >0.5 LNR. KaplanMeier methodswere used to assess survival differences (up to 10 years from diagnosis) according to LNR status. Cox proportional hazards models were constructed to evaluate differences in prognosis after controlling for potential confounders. Results: We identified 3,079 patients surgically resected N1M0 SI-NETs. The mean (standard deviation) patient age was 61.4±12.6 years, 53% were male, and 80% were white. Overall, 59% of cancers were located in the ileum, 5% in the duodenum, and 6% in the jejunum. NET cancer-specific survival was lower among patients with a high LNR (p 0.5 LNR groups, respectively (Figure 1). Adjusted analyses also showed that a higher LNR was associated with worse disease-specific survival. Compared with patients in the lowest LNR group (≤0.15), the hazard of NET-related death was 1.33 (95% Confidence Interval [CI] 0.91-1.87) and 1.59 (95% CI 1.05-2.13) times greater for patients in the 0.160.6 and >0.5 LNR categories, respectively. Conclusions: Extent of LN involvement provides independent prognostic information in patients with LN positive SI-NETs. This information may be used to identify patients at high risk of recurrence and inform therapy.