The Prognostic Role of PORT and EGFR Mutation Status in Completely Resected Stage IIIA/N2 Non-Small Cell Lung Cancer Patients with Postoperative Chemotherapy

Background: The treatment choice for completely resected stage IIIA/N2 non-small cell lung cancer (NSCLC) patients is still controversial now. Our study aims to identify potential prognostic factors in stage IIIA/N2 NSCLC patients with complete surgical resection and postoperative chemotherapy. Methods: In this study, we screened the stage IIIA/N2 NSCLC patients diagnosed in the Affiliated Cancer Hospital of Zhengzhou University from 2015 to 2019. Completely resected patients with postoperative chemotherapy (PCT) were enrolled. The univariate and multivariate COX proportional hazards regression analyses were used to identify the prognostic factors. The Kaplan-Meier survival curve was used to compare the disease-free survival (DFS) and overall survival (OS) in the subgroup analyses. Results: 180 patients were collected, including 142 patients with PCT treatment alone and 38 patients with postoperative radiotherapy (PORT) treatment. The median DFS was 17.8 months (95% CI: 16.5-19.1 months) and the median OS was 50.6 months (47.4-53.9 months) in all the patients. The median DFS of the PORT group was significantly longer than the PCT group (38.7 vs 16.7 months, p < 0.001). Epidermal growth factor receptor (EGFR) mutation-positive patients had a worse DFS compared with EGFR mutation-negative patients (16.8 vs 18.0 months, p = 0.032). Possible prognostic factors were evaluated through univariate COX regression analysis. The further multivariate COX regression analysis showed that patients with PORT (HR: 0.318, 95% CI: 0.185-0.547, p < 0.001), EGFR mutation-negative (HR: 0.678, 95% CI: 0.492-0.990, p = 0.044), T1 (HR: 0.661, 95% CI: 0.472-0.925, p = 0.016), and lobectomy (HR: 0.423, 95% CI: 0.191-0.935, p = 0.034), had better DFS. The only independent prognostic factor of OS was the type of surgery (p = 0.013). Conclusion: PORT might improve the DFS of stage IIIA/N2 NSCLC patients with complete surgical resection and PCT, but it cannot increase OS. Besides, EGFR mutation status, T stage, and type of surgery are possible independent prognostic factors for DFS, and type of surgery is associated with OS. These factors remain to be clarified in further studies.