Evaluation of Risk Factors for Vertebral Compression Fracture after Stereotactic Radiosurgery in Spinal Tumor Patients

OBJECTIVE Stereotactic radiosurgery (SRS) is an emerging treatment modality for malignant spinal tumors. After SRS, some patients suffered from pain aggravation due to development of vertebral compression fracture (VCF). In these cases, surgery should be considered. METHODS This study consisted of 72 patients who underwent SRS due to spinal tumors. In them, whether post-SRS VCF developed or not was investigated. We retrospectively analyzed their medical records and radiological imaging data. VCF was diagnosed with X-ray and magnetic resonance imaging (MRI). The incidence, time to development and risk factors for VCF were investigated. Age, sex, whole vertebral body involvement rate, vertebral body osteolysis rate, pre-SRS spinal deformity, spinal instability neoplastic score (SINS), spinal canal encroachment, lesion level, and radiation dose were analyzed as potential risk factors. A multi-variate logistic regression model was used for statistical analysis. RESULTS In our study population, VCF was observed in 26 patients (36%). The mean time to VCF development was 1.5 months. Using uni-variate analyses, the significant risk factors were pre-SRS spinal deformity, SINS, vertebral body osteolysis rate, and whole vertebral body involvement rate. However, using multi-variate analyses, the only significant risk factor was vertebral body osteolysis rate. The patients whose vertebral body was destroyed by more than 60% showed an 8.4 times higher risk of VCF than those who had vertebral body destruction of less than 60%(p=0.016). CONCLUSION The most significant prognostic factor for post-SRS VCF was vertebral body osteolysis rate, rather than whole vertebral body involvement rate. When more than 60% of the vertebral body was destroyed, the risk of VCF or spinal deformity was high.