The Number of Lymph Nodes Examined is Associated with Survival Outcomes of Neuroendocrine Tumors of the Jejunum and Ileum (siNET): Development and Validation of a Prognostic Model Based on SEER Database

Purpose The number of neuroendocrine tumors (NETs) is gradually increasing worldwide, and those located in the small intestine (siNETs) are the most common. As some biological and clinical characteristics of tumors of the jejunum and the ileum differ, there is a need to assess the prognosis of individuals with siNETs of the jejunum and ileum separately. We generated a predictive nomogram by assessing individuals with siNETs from the Surveillance, Epidemiology, and End Results (SEER) database. Methods We used univariate Cox regression analysis to determine both the overall survival (OS) and the cancer-specific survival (CSS) of 2501 patients with a pathological confirmation of siNETs of the jejunum and ileum. To predict 3-, 5-, and 10-year OS of siNETs, a nomogram was generated based on a training cohort and validated with an external cohort. Accuracy and clinical practicability were evaluated separately by Harrell’s C-indices, calibration plots, and decision curves. The correlation was examined between dissected lymph nodes and positive lymph nodes. Results Dissection of 7 or more lymph nodes significantly improved patient OS and was found to be a protective factor for patients with siNETs. In Cox regression analyses, age, primary site, tumor size, N stage, M stage, and regional lymph node examination were significant predictors in the nomogram. A significant positive correlation was found between dissected lymph nodes and positive lymph nodes. Conclusions Patients with 7 or more dissected lymph nodes showed an accurate tumor stage and a better prognosis. Our nomogram accurately predicted the OS of patients with siNETs.