The association of postoperative radiotherapy with survival in resected N2 non-small cell lung cancer

BACKGROUND: The current staging system for completely resected pathologic N2 non-small cell lung cancer (NSCLC) treated with chemotherapy is not suitable for distinguishing those patients most likely to benefit from postoperative radiotherapy (PORT). This study aimed to construct a survival prediction model that will enable individualized prediction of the net survival benefit of PORT in patients with completely resected N2 NSCLC treated with chemotherapy. METHODS: A total of 3,094 cases from between 2002 and 2014 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Patient characteristics were included as covariates, and their association with overall survival (OS) with and without PORT was assessed. Data from 602 patients from China were included for external validation. RESULTS: Age, sex, the number of examined/positive lymph nodes, tumor size, the extent of surgery, and visceral pleural invasion (VPI) were significantly associated with OS (P<0.05). Two nomograms were developed based on clinical variables to estimate individuals’ net survival difference attributable to PORT. The calibration curve showed excellent agreement between the OS predicted by the prediction model and that actually observed. In the training cohort, the C-index for OS was 0.619 [95% confidence interval (CI): 0.598–0.641] in the PORT group and 0.627 (95% CI: 0.605–0.648) in the non-PORT group. Results showed that PORT could improve OS [hazard ratio (HR): 0.861; P=0.044] for patients with a positive PORT net survival difference. CONCLUSIONS: Our practical survival prediction model can be used to make an individualized estimate of the net survival benefit of PORT for patients with completely resected N2 NSCLC who have been treated with chemotherapy.