The lymph node status and histologic subtypes influenced the effect of postoperative radiotherapy on patients with N2 positive IIIA non-small cell lung cancer

Background and Objective To investigate the role of postoperative radiotherapy (PORT) in IIIA-N2 non-small cell lung cancer (NSCLC) patients and subgroups which derived benefit from PORT. Methods A total of 576 patients with pathological IIIA-N2 NSCLC, who underwent complete resection, were identified. Propensity score matching (PSM) methods were used to balance the patients' characteristics between two groups. Overall survival (OS) and relapse-free survival (RFS) were compared between PORT and non-PORT patients. Results On multivariable analysis, improved OS remained correlated with younger age, single N2 station involvement, less positive lymph nodes, and chemotherapy. After PSM, 121 PROT patients and 242 non-PORT patients were matched. PORT was not associated improved patients' OS (P = 0.735) or RFS (P = 0.483). For patients who underwent postoperative chemotherapy (POCT), PORT could improve OS in single N2 station involved patients (HR: 0.572, 95%CI: 0.312 to 1.05, P = 0.040). Patients with papillary predominant adenocarcinoma also benefited from PORT with an increase in OS (HR: 0.350, 95%CI: 0.126 to 0.972, P = 0.033). Conclusions For patients with completely resected IIIA-N2 NSCLC, mediastinal lymph node metastasis and histologic subtypes could influence the effect of PORT. Single N2 station involvement and papillary predominant subtype were predictors of benefit from PORT.