Stereotactic Radiation Therapy (SBRT) Versus External Beam (EB) Radiation for Metastatic Spine Disease: Comparing Fracture Rates and Local Control

Abstract

Abstract INTRODUCTION Stereotactic radiation therapy (SBRT) is often preferred to external beam (EB) radiation because it provides a higher radiation dose and reduces need for retreatment to the same site. Although SBRT is regarded as a viable option, there is no research comparing fracture rates and disease progression to EB radiation. METHODS Records from patients treated at our hospital for metastatic spine disease were retrospectively reviewed. Mortality, local disease progression (resulting in additional intervention or radiographic progression), and vertebral body fractures were compared between SBRT and EB radiation. A total of 96 and 213 patients were identified for SBRT and EB groups respectively. Multivariate regression identified the need to control for tumor histology, follow-up time (in months), and age at therapy. The patient-matched EB comparison group was made by matching SBRT cases on propensity scores for confounders. Matching resulted in 70 SBRT-EB cases. RESULTS Following the matching process, balance of the covariates (age at therapy, follow-up time, and primary tumor histology) was confirmed between groups (P = .136, P = .596 respectively and matched tumor histology). The SBRT group did not significantly differ in mortality rates and local disease progression compared to the EB group (P = .731, P = .847 respectively). However, the SBRT group did have a higher rate of vertebral body fracture: 14.2% compared to 4.2% in the EB group (P < .01). Multivariate analysis was used to account for potentially confounding effects of dose using biologically equivalent doses calculated with a/ß of 10 (ie, BED10) for acute toxicity and 3 (ie, BED3) for late toxicity, but did not affect results. CONCLUSION The data suggest that receiving SBRT for the treatment of metastatic spine disease may increase risk for vertebral body fracture compared to EB treatment. There were no differences in local disease progression or mortality.