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.