Postoperative Radiotherapy in Pathological T2-3N0M0 Thoracic Esophageal Squamous Cell Carcinoma: Interim Report of a Prospective, Phase III, Randomized Controlled Study.

BACKGROUND:The role of postoperative radiotherapy in pathological T2-3N0M0 esophageal squamous cell carcinoma is unknown. We aimed to evaluate the efficacy and safety of postoperative radiotherapy in patients with pathological T2-3N0M0 thoracic esophageal squamous cell carcinoma. MATERIALS AND METHODS:Patients aged 18-72 years with pathological stage T2-3N0M0 esophageal squamous cell carcinoma after radical surgery and without neoadjuvant therapy were eligible. Patients were randomly assigned to surgery alone or to receive postoperative radiotherapy of 50.4 Gy in supraclavicular field and 56 Gy in mediastinal field in 28 fractions over 6 weeks. The primary endpoint was disease-free survival. The secondary endpoints were local-regional recurrence rate, overall survival, and radiation-related toxicities. RESULTS:From October 2012 to February 2018, 167 patients were enrolled in this study. We analyzed 157 patients whose follow-up time was more than 1 year or who had died. The median follow-up time was 45.6 months. The 3-year disease-free survival rates were 75.1% (95% confidence interval [CI] 65.9-85.5) in the postoperative radiotherapy group and 58.7% (95% CI 48.2-71.5) in the surgery group (hazard ratio 0.53, 95% CI 0.30-0.94, p = .030). Local-regional recurrence rate decreased significantly in the radiotherapy group (10.0% vs. 32.5% in the surgery group, p = .001). The overall survival and distant metastasis rates were not significantly different between two groups. Grade 3 toxicity rate related to radiotherapy was 12.5%. CONCLUSION:Postoperative radiotherapy significantly increased disease-free survival and decreased local regional recurrence rate in patients with pathological T2-3N0M0 thoracic esophageal squamous cell carcinoma with acceptable toxicities in this interim analysis. Further enrollment and follow-up are warranted to validate these findings in this ongoing trial. IMPLICATIONS FOR PRACTICE:The value of adjuvant radiotherapy for patients with node-negative esophageal cancer is not clear. The interim results of this phase III study indicated that postoperative radiotherapy significantly improved disease-free survival and decreased local-regional recurrence rate in patients with pathological T2-3N0M0 thoracic esophageal squamous cell carcinoma compared with surgery alone with acceptable toxicities. The distant metastasis rates and overall survival rates were not different between the two groups. Adjuvant radiotherapy should be considered for pathologic T2-3N0M0 thoracic esophageal squamous cell carcinoma. Prospective trials to identify high-risk subgroups are needed.