Pretreatment Factors Influencing Radiation Pneumonitis after Stereotactic Body Radiation Therapy in the Treatment of Lung Cancer

Objective Radiation pneumonitis (RP) is a dose-limiting toxicity that affects the treatment of lung cancer. Data on factors predictive of developing symptomatic RP after stereotactic body radiation therapy (SBRT) are limited. We reviewed data to identify pretreatment factors predictive of the development of symptomatic RP in patients' lung cancer treated with SBRT. Methods Data were collected on 296 patients treated with SBRT for lung cancer. Factors available at time of consultation were analyzed for the development of symptomatic RP, defined as CTCAE v. 4.0 >= Grade 2. The factors analyzed included patient demographic, tumor-specific, and pretreatment pulmonary function data. Univariate and multivariate analyses were performed to assess for predictive factors. Results Median follow-up was 22 months. The rate of symptomatic RP was 16%. Univariate analysis showed an increased rate of symptomatic RP with treatments to the right lung (22% vs. 9%, p = 0.007), driven primarily by an increased rate of symptomatic RP when treating the right lower lobe (RLL) vs. other lobes (31 vs. 13%, p = 0.03). Patients with a history of prior lung directed therapy were also more likely to develop symptomatic RP (12% vs. 24%, p = 0.008). These statistical differences were retained on multivariate analysis. Conclusion SBRT to the right lung, especially the RLL, and to patients with a history of prior lung-directed therapy increases the risk of developing symptomatic RP after SBRT. Further studies on ways to predict and prevent symptomatic RP are needed.