Trends and Costs of Stereotactic Body Radiation Therapy in Metastatic Non-Small Cell Lung Cancer

Abstract

Stereotactic Body Radiation Therapy (SBRT) has emerged as a therapeutic option in patients with oligometastatic non-small cell lung cancer (NSCLC). Currently, the patterns of care of SBRT in elderly metastatic NSCLC patients are not known. Similarly, the impact that SBRT has on the overall frequency and costs of hospitalizations are not known. The purpose of this project is to describe early SBRT use, outcomes, hospitalizations and their costs, as compared to matched patients receiving chemotherapy among patients with metastatic NSCLC.Using the SEER-Medicare database, we identified 215 patients with metastatic NSCLC who received SBRT as first line treatment and 12,486 patients who received chemotherapy between 2004 and 2014. We limited our sample to patients ≥66 years to have a full year of Medicare claims to determine pre-existing co-morbidities and disability score prior to their diagnosis. We excluded patients who had brain metastases, cancer-directed surgery, or survived less than 30 days from diagnosis. Multivariable logistic regression was used to identify covariates associated with SBRT use. Overall survival between SBRT and chemotherapy was compared using Cox proportional hazards regression and the Kaplan-Meier estimator. In order to compare hospitalizations and associated costs, we matched patients treated with SBRT to those receiving chemotherapy with comparable prognostic factors. All statistical tests were two-sided.Median age was 74. SBRT use as first line treatment increased from 0.5% to 3% over the study period. SBRT use was independently associated with older age (OR 1.09, P < 0.001), female sex (OR 1.54, P = 0.002), poor disability status (OR 2.09, P < 0.001), and lower T- and N-stage (P < 0.001). Survival increased with SBRT use (HR 0.72, P < 0.001), female sex (HR 0.80, P < 0.001) higher income (≥$80,000, HR 0.85, P < 0.001) and decreased with higher Charlson Comorbidity Score (≥2, HR 1.09, P < 0.001), poor disability status (HR 1.22, P < 0.001), higher T-stage (HR 1.31, P < 0.001) and higher N-stage (N3, HR 1.21, P < 0.001). Among a sample matched on age, sex, Charlson comorbidity score, disability status, T-stage and N-stage, patients treated with first line SBRT underwent fewer hospitalizations compared to chemotherapy patients (73% vs. 81%, P < 0.01) however, SBRT patients incurred higher total hospitalization costs (mean $33,039 vs. $23,709, P < 0.001). The most common admitting diagnoses were shortness of breath and pneumonia.In a sample of elderly Medicare patients, the use of SBRT among patients with metastatic lung cancer is increasing. Despite these patients having worse prognostic factors (e.g., older age, poor disability status), receipt of SBRT was associated with improved survival compared to chemotherapy. SBRT was associated with overall fewer hospitalizations but increased hospitalization costs, possibly reflecting more complex management of treatment-related complications.