Long-term Clinical Outcomes and Safety Profile of SBRT for Centrally Located NSCLC

Purpose: Previous studies suggest that stereotactic body radiation therapy (SBRT) is associated with higher toxicity rates for central lung tumors relative to peripheral tumors when using 3 fraction SBRT. The initial results from Radiation Therapy Oncology Group study 0813 suggest a safe toxicity profile of SBRT administered in 5 fractions for central non-small cell lung cancer (NSCLC). We reviewed our institutional data to evaluate the safety and efficacy of SBRT for central NSCLC. Methods and materials: We reviewed our prospectively collected SBRT database for patients with central NSCLC who received SBRT between 2008 and 2014. The most frequent dose and fractionations were 50 Gy in 5 fractions (59%) and 48 Gy in 4 fraction (30%). Local control (LC), regional control, metastasis-free survival, and overall survival were calculated using Kaplan-Meier estimates. The National Cancer Institute Common Terminal Criteria for Adverse Events were used for toxicity grading. Results: A total of 110 central lung tumors in 103 patients were included. The median age was 74 years (range, 40-95 years), and the median follow-up time of living patients was 50 months. The mean tumor size was 20 mm (range, 5-70 mm). The 5 year rate of LC, regional control, and distant control was 89%, 77%, and 82%, respectively. The median and 5-year overall survival were 3.5 years and 35%, respectively. No treatment variables were associated with tumor control or other clinical outcomes. A single patient experienced grade 3 radiation pneumonitis (0.97%). The rate of late toxicity grade ≥3 was 9.7% (grade 3, 7.7%; grade 4, 0.97%; grade 5, 0.97%) and included pneumonitis (3.9%), bronchial necrosis (2.9%), myocardial dysfunction (1.9%), and worsening heart failure (0.97%). Conclusions: SBRT for central NSCLC provides high rates of LC. Despite excellent LC, patients remain at risk for regional and distant failure. The rate of grade 3 pneumonitis was consistent with that of prior reports. We observed low rates of grade 4-5 toxicity potentially attributable to SBRT. Our results contribute to the growing body of data in support of the safety of SBRT for central NSCLC.