Validated Risk-Score Model Predicting Lymph Node Metastases in Patients with Non-Functional Gastroenteropancreatic Neuroendocrine Tumors.

BACKGROUND The incidence of, and factors associated with, lymph node metastasis (LN+) in non-functional gastroenteropancreatic (GEP) neuroendocrine tumors (NETs) are not well characterized. METHODS Patients were identified from the 2010-2015 National Cancer Database who underwent surgical resection with lymphadenectomy for clinical stage I-III non-functional GEP NETs. Among a randomly selected training subset of 75% of the study population, variables associated with LN+ were identified using multivariable logistic regression analysis, and these variables were used to create a risk-score model for LN+, which was internally validated among the remaining 25% of the cohort. RESULTS Of 12,228 patients evaluated, 6,902 (56.4%) had LN+. Among the training set, variables associated with LN+ included age (70 years of age or older: odds ratio [OR] 1.12, 95% CI 1.00-1.24; ref: less than 70 years), tumor location (stomach: OR 3.72, 95% CI 2.94-4.71; small intestine: OR 19.60, 95% CI 17.31-22.19; ref: pancreas), tumor grade (moderately differentiated: OR 1.47, 95% CI 1.30-1.67; poorly differentiated/anaplastic: OR 1.53, 95% CI 1.21-1.95; ref: well-differentiated), tumor size (2-4 cm: OR 2.40, 95% CI 2.13-2.70; >4 cm: OR 5.25, 95% CI 4.47-6.17; ref: <2 cm), and lymphovascular invasion (OR 5.62, 95% CI 5.08-6.21; ref: no lymphovascular invasion). After internal validation, a risk-score model for LN+ using these variables was developed composed of low- (N = 2,779), intermediate- (N = 2,598), high- (N = 3,433), and very-high-risk (N = 3,418) groups; within each group the rate of LN+ was 8.7%, 48.6%, 64.9%, and 92.8%, respectively. CONCLUSIONS This developed risk-score model, including both patient and tumor variables, can be used to calculate the risk for LN metastases in patients with GEP NETs.