A monocentric retrospective analysis of 10-year overall survival after stereotactic body radiotherapy for medically inoperable non-small cell lung cancer.

Stereotactic body radiation therapy (SBRT) is widely used to treat inoperable non-small cell lung cancer (NSCLC). The present study analyzed the long-term (10-year) survival outcomes of patients with NSCLC treated with SBRT in a real-world setting. Patients with NSCLC treated with SBRT between 2009 and 2013 were retrospectively identified from institutional databases at the Department of Radiation Oncology, University Hospital Halle (Saale) [Halle (Saale), Germany]. Comorbidities were assessed using the Charlson comorbidity index (CCI) and the age-adjusted CCI. Kaplan-Meier curves were generated to estimate overall survival (OS) and group comparisons were performed using the log-rank test. Prognostic factors including age, sex, Karnofsky performance status (KPS), histological subtype, tumor grading, T- and N-stage, PET-based treatment planning, mean biologically effective dose (BEDmean/Gy(10)), gross tumor volume (GTV) and CCI were analyzed. Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI). Variables that were significant in the univariate analysis were entered into a multivariate stepwise regression model. A sensitivity analysis with multiple imputations was performed to assess the robustness of the findings. P<0.05 was considered to indicate a statistically significant difference. A total of 58 patients with NSCLC with M0-status were included in the present analysis. The 3-, 5- and 10-year OS rates were 35.09, 24.56 and 8.77%, respectively. The median OS was 32 months (95% CI, 10-35). In the univariate Cox regression, age ≥75 years was significantly associated with improved survival (HR, 0.54; 95% CI, 0.31-0.92; P=0.025), though this effect was not statistically significant in the multivariate model (HR, 0.55; 95% CI, 0.30-1.01; P=0.057). The KPS (≤70 vs. >70%), sex and the age-adjusted CCI showed no significant association with OS. BEDmean, dichotomized at 120.31 Gy(10), was not significantly associated with OS in the multivariate model (P=0.2), although the Kaplan-Meier analysis showed a significant survival difference (P=0.011). By contrast, larger GTV (>25.6 cm(3)) was independently associated with worse survival in both the univariate (HR, 1.01; 95% CI, 1.00-1.02; P=0.041) and multivariate (HR, 1.01; 95% CI, 1.00-1.02; P=0.024) analyses. These findings were confirmed in a sensitivity analysis using multiple imputations, supporting the robustness of age and GTV as prognostic factors for NSCLC patients treated with SBRT. SBRT provides moderate long-term survival in patients with NSCLC. Older patients (≥75 years) showed favorable outcomes. Tumor volume was the strongest prognostic factor, while BEDmean and performance status were not independently associated with survival.