Participants will be evaluated for inclusion criteria and exclusion criteria, and then sign informal consent if desired. Participants will be randomly assigned to the intervention according to a prepared random tables. Participants in the systematically mediastinal lymph node dissection (SLND) group will receive systematically mediastinal lymph node dissection, while those in the non-SLND group will not receive mediastinal lymph node dissection. The primary endpoint is 3-year disease-free survival (DFS).
The sample size are estimated with reference to investigators' previous data, in which the 3-year DFS was 62.7% for patients diagnosed with T1a Stage Esophageal Squamous Cell Carcinoma and underwent Endoscopic Submucosal Dissection without SLND. Investigators assumed that if 3-year DFS of patients in SLND group was over 80%, then investigatorswould deem the SLND group to be superior to the non-SLND group. The sample size are estimated to be 102. Therefore, the total number of patients enrolled are designed to be 102.