Predictors of Distant Failure After Stereotactic Body Radiation Therapy for Stages I to IIA Non-Small-Cell Lung Cancer

Stereotactic body radiation therapy (SBRT) is an effective treatment modality for early-stage non small-cell lung cancer, with excellent rates of local control. Despite this, the predominant pattern of failure in these patients is distant. We sought to identify factors that may help to predict which of these patients are at highest risk of distant failure following SBRT. We retrospectively reviewed 292 patients treated with SBRT for earlystage non small-cell lung cancer. The primary endpoint was distant failure. We classified patients according to T-stage, tumor size, location and histology, pretreatment positron emission tomography/computed tomography standardized uptake value, smoking status, and age. The 2-year distant failure rate was 22.0%, and the 2-year overall survival was 61.0%. For every 1-year increase in patient age, the hazard of distant failure at any given time was 3% lower (hazard ratio, 0.97; 95% confidence interval, 0.94-0.99; P = .04). No other clinical factors emerged as significant predictors, and additional molecular studies may be needed to identify the patients with early-stage lung cancer at highest risk of distant failure. Purpose: The use of stereotactic body radiation therapy (SBRT) has emerged as an effective treatment modality for patients with early-stage non-small-cell lung cancer (NSCLC), with excellent local control rates. Despite this, there is a predominant pattern of distant failure. We sought to identify factors that help predict which patients with stages I to II A NSCLC treated with SBRT are at highest risk of distant failure, so that we may utilize these factors in the future to help determine which patients may benefit from the addition of systemic therapies. Patients and Methods: We retrospectively reviewed 292 patients treated with SBRT for early stage NSCLC from 2006 to 2016 at 2 institutions. Patients were classified by T stage, tumor size, location and histology, pretreatment positron emission tomography/computed tomography (PET/CT) standardized uptake value (SUV), smoking status, and age. The primary endpoint of the study was distant failure. We aimed to analyze if patient characteristics could be identified that predicted for distant failure through the use of competing risk analysis. Results: The median follow-up was 21.9 months. The median dose of radiation and fractionation delivered was 50 Gy (range, 45-65 Gy) in 5 fractions (range, 3-13 fractions). The median patient age was 72.8 years (interquartile range, 65.4-79.7 years). The 2-year distant failure was 22.0%, and overall survival at 2 years was found to be 61.0%. For every 1year increase in patient age, the hazard of distant failure at any given time was 3% lower (hazard ratio, 0.97; 95% confidence interval, 0.94-0.99; P = .04). None of the remaining characteristics emerged as significant risk factors for distant failure on univariable or multivariable analysis. Conclusions: Overall, our cohort had distant failure and survival rates comparable with what has been described in the literature. Although we were unable to identify factors outside of age that correlated to risk of distant failure, this topic warrants further investigation, as distant failure is the primary pattern of failure with SBRT when used as the primary management for early-stage NSCLC. Additional molecular studies are needed to further inform on the role of systemic therapy in patients with early-stage NSCLC to improve clinical outcomes. Published by Elsevier Inc.