Determining the Adequate Examined Lymph Node Count in Resected Ampullary Adenocarcinoma—A National Cohort Study

Background: The evaluation of lymph node involvement is an essential component of cancer staging. Examining an inadequate number of lymph nodes potentially results in understaging. Current guidelines for lymph node retrieval for ampullary adenocarcinoma are based on data extrapolated from other periampullary malignancies and may not be applicable. The aim of this study was to determine the number of lymph nodes that should be examined in resection specimens to optimize staging in ampullary adenocarcinoma. Methods: Patients with ampullary adenocarcinoma from 2004 to 2014 were identified in the National Cancer Database. We determined the minimum examined lymph node (ELN) count by modeling each potential ELN count from 2 to 30 in a multivariable regression analysis and confirmed the results with a sensitivity analysis. Results: We identified 7451 patients of whom 52.2% had T3 or T4 disease and 51.4% had lymph node metastases. The median ELN count was 13 (interquartile range, 8–19). Increasing ELNs were independently associated with an increased likelihood of having positive nodal disease (odds ratio, 1.03; 95% confidence interval [CI], 1.03–1.04) and improved overall survival in both node-negative (hazard ratio [HR], 0.98; 95% CI, 0.97–0.99) and node-positive patients (HR, 0.99; 95% CI, 0.986–0.998). We determined that at least 17 lymph nodes should be examined. Overall survival for patients with 17 or more ELNs was superior than for those with fewer than 17 ELNs. Conclusion: Increasing ELNs were independently associated with improved overall survival in patients with resected ampullary adenocarcinoma. At least 17 lymph nodes should be examined for optimal nodal staging.