Introduction: A staple of current treatment paradigm of spinal metastasis is radiosurgery as the primary modality, reserving surgery for highgrade epidural spinal cord compression or spinal instability. Multiple studies report vertebral body compression fracture rates from 1139% after SBRT. Reports of patients’ pain control ranged from 5285% at 12 months and local control rates of 8795% at 6 months to 7392% at 12 months. Studies have shown that with high treatment doses the fracture rates are higher. We describe our experience of lowdose SBRT for spinal metastasis with fracture rates, local and pain control.
Methods: This is a retrospective, single institution analysis of 134 patients (316 spinal segments) undergoing SBRT for spinal metastases from 2010 2015. Fracture rates were assessed on followup CT. Local control analysis conducted with KaplanMeier statistics.
Results: 127 patients (287 spinal segments) were included in the analysis. Median age 67 years. Location of tumors were 13% cervical, 49% thoracic, 34% lumbar, 4% sacral. Tumor histology was 57.8% radiosensitive and 42.2% radioresistant. Treatment doses were: 13-20Gy single-fraction (52%); 16-27Gy 3-fraction (37%); and 25-40Gy 5-fraction (11%). 19% spinal levels required separation surgery for high-grade epidural-spinal-cord-compression. Patient-reported pain scores showed 36% improved, 43% stable, and 20% worsened. Fracture rates were 9.06%. Local control rates were 83% at 6months and 76% at 12months. Local failure rates better in singlefraction versus hypofractionated (HR=2.63; p=0.01). There was no difference between radiosensitive and radioresistant tumors in local control (HR=1.59; p=0.26). Better local control with SINS 0-6 vs >7 (HR=4.25; p=0.004).
Conclusions: Lowdose SBRT can achieve durable radiologic local and pain control in spinal metastatic disease. Fracture rates can be lowered with this approach, while still balancing appropriate local and pain control. Single fraction treatment is superior to multifraction regimens. Multidisciplinary treatment teams can entertain lowdose regimens for patients at higher risk for vertebral body fractures.
Patient Care: Patients at higher risks of vertebral body fractures can be administered low dose radiation to minimize fractures. This can lead to improved pain and quality of life which is paramount in patients with metastatic disease.
Learning Objectives: (1) Describe the effect of SBRT dose on vertebral body fracture rates. (2) Identify effective treatment options to reduce vertebral body fracture rates.
(3) Identify the ability to of lowdose SBRT to obtain similar local control and pain control as higher doseSBRT.
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