Effects of Postoperative Radiotherapy on Survival of Patients With Stage IIIA Resected Non–Small Cell Lung Cancer: Analysis of the SEER Database

Background: The role of postoperative radiotherapy (PORT) in patients with resected stage IIIA non–small cell lung cancer (NSCLC) remains controversial. The purpose of this study was to explore the effect of PORT on survival of these patients. Methods: Patients aged ≥18 years with stage IIIA NSCLC were identified in the SEER database from 2010 through 2015. Cox regression analysis was used to identify independant prognostic factors in patients with stage IIIA NSCLC. Subgroup analysis of patients stratified by N stage was also performed. Overall survival and lung cancer–related death were compared among the different groups by using Kaplan-Meier analysis and competitive risk analysis. Results: A total of 5,168 patients (1,711 of whom received PORT) were included in the study. In multivariable analysis, PORT was an independent prognostic risk factor for patients with N1 stage (hazard ratio [HR], 1.416, 95% CI, 1.144–1.753; P =.001). PORT was a favorable prognostic factor for patients with stage IIIA, N2 disease with ≥6 positive lymph nodes (HR, 0.742; 95% CI, 0.587–0.938; P =.012). Median survival time of patients with stage IIIA, N2 disease with ≥6 positive lymph nodes who received postoperative chemotherapy combined with PORT was significantly longer compared with those who received postoperative chemotherapy alone (32 vs 25 months, respectively; P =.009). The competitive risk model revealed that 3- and 5-year lung cancer–related mortality rates increased by 8.99% and 16.92%, respectively, in patients with N1 disease who were treated with PORT, whereas the 3-year mortality rate decreased by 4.67% and the 5-year mortality rate by 10.08% in patients with N2 disease and ≥6 positive lymph nodes who were treated using PORT. Conclusions: Our results revealed that PORT significantly improved overall survival and decreased lung cancer–related mortality in patients with stage IIIA, N2 disease with ≥6 positive lymph node metastases. PORT was not recommended for patients with N0 and N1 disease.