Impact of Examined Lymph Node Count for Esophageal Squamous Cell Carcinoma in Patients who Underwent Right Transthoracic Esophagectomy

Background. The impact of the number of examined lymph nodes (ELNs) on stage correction and prognostication in patients with esophageal squamous cell carcinoma (ESCC) who underwent right transthoracic esophagectomy is still unclear. Methods. Patients with ESCC who underwent right transthoracic esophagectomy at Sun Yat-sen University Cancer Center between January 1997 and December 2013 were retrospectively enrolled. The Cox proportional hazards regression model was used to determine the effect of ELN count on overall survival. The impact of ELN count on stage correction was evaluated using the hypergeometric distribution and Bayes theorem and beta-binomial distribution estimation, respectively. The threshold of ELNs was determined using the LOWESS smoother and piecewise linear regression. Results. Among the 875 included patients, greater ELNs were associated with a higher rate of nodal metastasis. Significant association between staging bias and the number of ELNs is only observed through the Bayes method. The ELN count did not impact 90-day mortality but significantly impacted long-term survival (adjusted hazard ratio [aHR] 0.986), especially in those patients with node-negative disease (aHR 0.972). In patients with node-negative disease, cut-point analysis showed a threshold ELN count of 21. Conclusions. A greater number of ELNs is associated with more accurate node staging and better long-term survival in resected ESCC patients. We recommended harvesting at least 21 LNs to acquire accurate staging and long-term survival information for patients with declared node-negative disease using the right thoracic approach.