Abstract
BACKGROUND/AIMS: Current staging guidelines for small intestinal neuroendocrine tumors (SI-NETs) differentiate 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 population-based 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 SI-NETS diagnosed between 1988 and 2010. Patients were classified into three groups by the LN ratio (number of positive LNs/number of total LNs examined, LNR): ≤0.2, >0.2-0.5, and >0.5. We used the Kaplan-Meier method and Cox models to assess NET cancer-specific survival differences (up to 10 years from diagnosis) according to LNR status. RESULTS: We identified 2,984 surgically resected patients with stage IIIb (N1, M0) SI-NETs with detailed LN data. More than half of the NETs were located in the ileum. A higher LNR was significantly associated with worse NET cancer-specific survival (p < 0.0001). Ten-year NET-specific survival was 85, 77, and 74% for patients in the ≤0.2, >0.2-0.5, and >0.5 LNR groups, respectively. In stratified analyses, higher LNR groups had worse survival only in early tumor (T1, T2) disease (p < 0.0001). CONCLUSIONS: The extent of LN involvement provides independent prognostic information on patients with LN-positive SI-NETs. This information may be used to identify patients at high risk of recurrence and inform decisions about the use of adjuvant therapy.