Impact of examined lymph node number on accurate nodal staging and long-term survival of resected Siewert type II-III adenocarcinoma of the esophagogastric junction: A large population-based study

BackgroundWe aimed to investigate the association between the number of examined lymph nodes (ELNs) and accurate nodal staging and long-term survival in Siewert type II-III Adenocarcinoma of the Esophagogastric Junction (AEG) by using large population-based databases and determined the optimal ELN number threshold. MethodsData on Stage I-III Siewert type II-III AEG patients from 2010 to 2014 respectively from the United States (US) SEER database and a Chinese large medical center institutional registry were analyzed for correlation between the ELN number and stage migration (node negative-to-positive) and overall survival (OS) by using multivariable-adjusted logistic and Cox regression models, respectively. The series of odds ratios (ORs), and hazard ratios (HRs) were fitted with a LOWESS smoother, and the structural breakpoints were determined by Chow test. The selected optimal cut point was then validated with the 2015 to 2016 SEER database. ResultsBoth the US cohort(n=1387) and China cohort(n=981) showed significantly increases from node-negative to node-positive disease (OR(theUS)1.032,95%CI 1.017-1.046;OR(China)1.034,95%CI 1.002-1.065) and enhancements in overall survival (HR(theUS)0.970,95%CI 0.961-0.979;HR(China)0.960,95%CI 0.940-0.980) with the increasing ELN number after controlling for confounders. Associations for both stage migration and overall survival were still significant in most subgroups' stratification. Cut point analysis showed a threshold ELN number of 18, which was validated both in the cohorts where it originated and in an independent SEER data cohort(n=379). ConclusionsMore ELNs are associated with accurate nodal staging(negative-to-positive) as well as higher overall survival in resected Siewert types II-III AEG, We recommend 18 ELNs as the optimal cut point for the quality assessment of postoperative lymph node examination or prognostic stratification in clinical practice.