Clinical Significance of Metastatic Lymph Nodes in the Gut of Patients with Pure and Mixed Primary Appendiceal Carcinoids

BACKGROUND: Right hemicolectomy is indicated for primary appendiceal carcinoids with diameters greater than 2 cm because of an increased risk of metastasis to the lymph nodes of the gut. However, the natural history of positive nodes remains unknown. OBJECTIVE: The aim of this study was to investigate the impact of metastatic lymph nodes on survival among patients with pure or mixed primary appendiceal carcinoids, while controlling for potential confounders such as age, sex, tumor size, surgical intervention, and lymph node rate (number of positive lymph nodes/lymph node yield). DESIGN: This is a retrospective comparative study.. SETTINGS: Data were retrieved from the Surveillance, Epidemiology and End Results database. PATIENTS: Patients undergoing colectomy for appendiceal carcinoids between 1998 and 2009 were selected. MAIN OUTCOME MEASURES: The survival curves for the 2 groups were compared to evaluate differences in prognosis. Univariate and multivariate analyses were performed. RESULTS: Lymph node rates did not significantly differ between the pure and mixed carcinoid groups (p = 0.768), although overall survival was poorer among patients with mixed carcinoids (p = 0.004; HR, 0.498; 95% CI, 0.310-0.800). For pure carcinoids, surgical intervention (p = 0.029; HR, 0.241; 95% CI, 0.067-0.867), age (p < 0.001; HR, 1.083; 95% CI, 1.051-1.116), and lymph node rate (p = 0.039; HR, 5.295; 95% CI, 1.089-25.754) were independent predictors of overall survival. For mixed carcinoids, surgical intervention (p = 0.019; HR, 1.675; 95% CI, 1.088-2.578), tumor size (p < 0.001; HR, 0.442; 95% CI, 0.286-0.683), age (p < 0.001; HR, 1.041; 95% CI, 1.026-1.056), and lymph node rate (p < 0.001; HR, 17.471; 95% CI, 10.047-0.382) were significant prognostic factors. LIMITATIONS: The study is limited by its retrospective nature and by the shortcomings of the Surveillance, Epidemiology and End Results database related to the availability and quality of data. CONCLUSION: Based on the data retrieved from the Surveillance, Epidemiology and End Results database and adjusted for potential confounding factors, the lymph node rate of metastasis strongly impacts overall survival among patients with pure or mixed carcinoids. Nodal metastasis thus appears to be a reliable clinical hallmark of tumor aggressiveness.