Purpose: To analyze the significance of the number of metastatic lymph nodes on survival with and without the addition of prophylactic postoperative radiotherapy (RT) after radical resection of thoracic esophageal carcinoma.
Methods and materials: A total of 549 thoracic esophageal squamous cell cancer patients who had undergone radical resection were randomized by the envelope method into a surgery-alone group (S, n = 275) and a surgery plus RT group (S+R, n = 274). We performed a retrospective review of all patients according to the extent of metastasis. The patients were classified into three groups: Group 1, 269 patients (49.0%) without lymph node involvement; Group 2, 159 patients (29.0%) with one to two positive nodes; and Group 3, 121 patients (22.0%) with three or more positive lymph nodes.
Results: For the same T stage (T3), the 5-year survival rate for Groups 1, 2, and 3 was 50.6%, 29.3%, and 11.7%, respectively (p = 0.0000). For patients with Stage III, the 5-year survival rate for Groups 1 (T4N0M0), 2 (T3-T4N1M0), and 3 (T3-T4N2M0) was 58.1%, 30.6%, and 14.4%, respectively (p = 0.0092). The 5-year survival rate of the S and S+R groups with positive lymph nodes (Groups 2 and 3) was 17.6% and 34.1% (p = 0.0378). In the positive lymph node groups, the incidence of failure by intrathoracic lymph node metastasis and supraclavicular lymph node metastasis in the S+R group (21.5% and 4.6%, respectively) was lower than in the S group (35.9% and 19.7%, respectively; p <0.012). In the negative lymph node group, the incidence of failure by intrathoracic lymph node metastasis in the S and S+R groups was 27.8% and 13.3%, respectively (p = 0.006). Hematogenous metastasis was the greatest (27.5%) in Group 3 (three or more positive lymph nodes).
Conclusion: The number of metastatic lymph nodes is one of the important factors affecting the survival of patients with thoracic esophageal carcinoma. In our study, postoperative RT improved the survival of patients with positive lymph nodes. Additionally, postoperative RT reduced the incidence of intrathoracic recurrence and supraclavicular lymph node metastasis for all patients.