Influence of negative lymph node in No 7 on survival of patients with middle thoracic esophageal squamous cell carcinoma

Background: The overall survival (OS) of patients with thoracic esophageal cancer is poor because of the high rate of lymph node metastases. However, recent studies found that the negative lymph node (LN) may also influence the patients' OS. The purpose of this study is to investigate which negative LN stations play a key role in OS prediction. Method: Our study included the retrospective records of 99 patients, who were identified with middle thoracic esophageal squamous cell cancer after esophagectomy. The maximum follow-up time was 6 years. Cox regression models were employed to determine the association between the negative LN and OS of patients. After applying Kaplan-Meier method to calculate OS of patients with positive and negative LNs, the log-rank tests were used to assess the difference between them. Result: The hazard ratio of the total number of negative LNs was 0.937 (P=0.001), and the length of tumor was 1.166 (P=0.038). Multivariate regression results showed that the numbers of positive LNs in No 3 and 7 stations and negative LNs in No 109 and 7 stations were significantly related to OS, and their P-values were 0.017, 0.001, 0.020, and 0.022, respectively. The OS of the patients who had positive and negative LNs in No 7 station was significantly different (P=0.028). Conclusion: No 7 is the most important among the negative LN stations which prolong OS. More attention should be paid to this area when making treatment plan for patients with no negative LNs identified in operation.