The emerging outcome of postoperative radiotherapy for stage IIIA(N2) non-small cell lung cancer patients: based on the three-dimensional conformal radiotherapy technique and institutional standard clinical target volume

BACKGROUND: The aim of this study was to evaluate the clinical efficacy of postoperative radiotherapy (PORT), administered using three-dimensional conformal radiotherapy (3D-CRT) and our institutional standard clinical target volume (CTV) delineation, for completely resected stage IIIA(N2) non-small cell lung cancer (NSCLC). METHODS: From 2005 to 2012, consecutive patients with pT1-3N2 NSCLC who were treated with PORT employing our institutional CTV delineation after complete surgery or who underwent complete resection in our hospital but without PORT were identified. We excluded patients who had received neoadjuvant chemotherapy or radiation therapy (RT). Kaplan-Meier estimates for locoregional recurrence-free survival (LRFS), distant metastasis-free survival (DMFS) and overall survival (OS) were performed. In the OS estimation, patients who received epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) during follow-up were censored at the time of TKI initiation. RESULTS: Data from 70 patients in the PORT group and 287 in the non-PORT group were analysed. All 70 cases received 3D-CRT following our institutional CTV guideline, with a median total dose of 50.4 Gy at 1.8 Gy/fraction. At a median follow-up of 34.3 months for the PORT group and 31.2 months for the non-PORT group, PORT significantly improved local control (5-yr LRFS 91.9% for PORT vs 66.4% for non-PORT, P < 0.001) and OS (5-yr OS 57.5% for PORT vs 35.1% for non-PORT, P = 0.003), whereas no differences in DMFS were noted (P = 0.18). In multivariable analyses, PORT was independently associated with an improved LRFS (HR 0.2, P = 0.001) and OS (HR 0.4, P = 0.001). All patients completed the planned RT dose without interruption of RT due to treatment-related complications. CONCLUSIONS: Our data suggested that PORT administered using the 3D-CRT technique following our institutional CTV delineation guideline resulted in a promising outcome with favourable survival for completely resected IIIA(N2) NSCLC, after controlling for subsequent EGFR-TKI confounding in the OS analysis. Prospective trials are needed to further corroborate these results.