clinical article J neurosurg Spine 24:928–936, 2016 abbreviationS ASIA = American Spinal Injury Association; D max = maximum dose; EQD 2 = equivalent 2-Gy dose; MDACC = MD Anderson Cancer Center; MSKCC = Memorial Sloan Kettering Cancer Center; SBRT = stereotactic body radiation therapy; SINS = Spinal Instability Neoplastic Score; VCF = vertebral compression fracture. SUbMitteD December 19, 2014. accePteD October 27, 2015. inclUDe when citing Published online February 19, 2016; DOI: 10.3171/2015.10.SPINE141261. Vertebral compression fractures after stereotactic body radiation therapy: a large, multi-institutional, multinational evaluation Maha Saada Jawad, MD, 1 Daniel K. Fahim, MD, 2 Peter c. gerszten, MD, 3,4 John c. Flickinger, MD, 3,4 arjun Sahgal, MD, 5 inga S. grills, MD, 1 Jason Sheehan, MD, 6 ronald Kersh, MD, 7 John Shin, MD, 8 Kevin oh, MD, 9 Frederick Mantel, MD, 10 and Matthias guckenberger, MD, 10,11 on behalf of the elekta Spine radiosurgery research consortium Departments of 1 Radiation Oncology and 2 Neurological Surgery, Oakland University William Beaumont School of Medicine, Royal Oak, Michigan; Departments of 3 Neurological Surgery and 4 Radiation Oncology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania; 5 Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Canada; 6 Department of Neurological Surgery, University of Virginia Health System, Charlottesville; 7 Department of Radiation Oncology, Riverside Medical Center, Newport News, Virginia; Departments of 8 Neurosurgery and 9 Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts; 10 Department of Radiation Oncology, University Hospital Wuerzburg, Germany; and 11 Department of Radiation Oncology, University of Zurich, Switzerland obJective The purpose of this study was to identify factors contributing to an increased risk for vertebral compres- sion fracture (VCF) following stereotactic body radiation therapy (SBRT) for spinal tumors. MethoDS A total of 594 tumors were treated with spinal SBRT as primary treatment or re-irradiation at 8 different insti- tutions as part of a multi-institutional research consortium. Patients underwent LINAC-based, image-guided SBRT to a median dose of 20 Gy (range 8–40 Gy) in a median of 1 fraction (range 1–5 fractions). Median patient age was 62 years. Seventy-one percent of tumors were osteolytic, and a preexisting vertebral compression fracture (VCF) was present in 24% of cases. Toxicity was assessed following treatment. Univariate and multivariate analyses were performed using a logistic regression method to determine parameters predictive for post-SBRT VCF. reSUltS At a median follow-up of 10.1 months (range 0.03–57 months), 80% of patients had local tumor control. At the time of last imaging follow-up, at a median of 8.8 months after SBRT, 3% had a new VCF, and 2.7% had a progres- sive VCF. For development of any (new or progressive) VCF following SBRT, the following factors were predictive for VCF on univariate analysis: short interval from primary diagnosis to SBRT (less than 36.8 days), solitary metastasis, no additional bone metastases, no prior chemotherapy, preexisting VCF, no MRI used for target delineation, tumor volume of 37.3 cm 3 or larger, equivalent 2-Gy-dose (EQD 2 ) tumor of 41.8 Gy or more, and EQD 2 spinal cord D max of 46.1 Gy or more. Preexisting VCF, solitary metastasis, and prescription dose of 38.4 Gy or more were predictive on multivariate analysis. The following factors were predictive of a new VCF on univariate analysis: solitary metastasis, no additional bone metastases, and no MRI used for target delineation. Presence of a solitary metastasis and lack of MRI for target delineation remained signifcant on multivariate analysis. conclUSionS A VCF following SBRT is more likely to occur following treatment for a solitary spinal metastasis, refecting a more aggressive treatment approach in patients with adequately controlled systemic disease. Higher pre- scription dose and a preexisting VCF also put patients at increased risk for post-SBRT VCF. In these patients, pre-SBRT cement augmentation could be considered to decrease the risk of subsequent VCF. http://thejns.org/doi/abs/10.3171/2015.10.SPINE141261 Key worDS radiosurgery; spinal tumors; stereotactic body radiotherapy; spine SBRT; vertebral fractures; oncology ©AANS, 2016 J neurosurg Spine Volume 24 • June 2016 928