Higher thoracic radiation dose is beneficial in patients with extensive small cell lung cancer

Purpose: The effectiveness of thoracic radiation therapy (TRT) in extensive-stage small cell lung cancer (ES-SCLC) patients is increasingly reported, but there is no definite consensus on its application. The aim of this study was to identify factors associated with better outcomes of TRT among patients with ES-SCLC, focusing on whether a higher TRT dose could improve treatment outcome. Materials and Methods: The medical records of 85 patients with ES-SCLC who received TRT between January 2008 and June 2017 were retrospectively reviewed. Eligibility criteria were a biological effective dose with alpha/beta = 10 (BED) higher than 30 Gy(10) and completion of planned radiotherapy. Results: During a median follow-up of 5.3 months, 68 patients (80.0%) experienced disease progression. In univariate analysis, a BED >50 Gy(10) was a significant prognostic factor for overall survival (OS; 40.8% vs 12.5%, p = 0.006), progression-free survival (PFS, 15.9% vs 9.6%, p = 0.004), and intrathoracic PFS (IT-PFS; 39.3% vs 20.5%, p = 0.004) at 1 year. In multivariate analysis, a BED >50 Gy(10) remained a significant prognostic factor for OS (hazard ratio [FIR] = 0.502; 95% confidence interval [CI] 0.287-0.876; p = 0.015), PFS (HR = 0.453; 95% CI, 0.265-0.773; p = 0.004), and IT-PFS (HR = 0.331; 95% CI, 0.171-0.641; p = 0.001). Response to the last chemotherapy was also associated with better OS in both univariate and multivariate analysis. Conclusion: A TRT dose of BED >50 Gy(10) may be beneficial for patients with ES-SCLC. Further studies are needed to select patients who will most benefit from high-dose TRT.