Early Experience With Two-Fraction Spine Stereotactic Body Radiation Therapy in Treating Spinal Metastases

Abstract

Introduction: Spinal metastases are common in metastatic cancer, affecting around 40% of patients. The primary treatment involves radiation therapy, transitioning from conventional external beam radiation therapy (EBRT) to stereotactic body radiation therapy (SBRT) for its superior, durable response. While spine SBRT has gained popularity in the United States, Level I evidence supporting it over EBRT is limited to a Canadian trial using a 2-fraction SBRT regimen. We present our findings from one of the earliest US experiences of 2-fraction spine SBRT for spinal metastases. Methods: A retrospective analysis of patients with metastatic spine cancer receiving 2-fraction spine SBRT at a single center was conducted. Patients received treatment based on Level 1 evidence (24 Gy in 2 fractions). Follow-up records were assessed for local control outcomes and toxicity. Results: Twenty patients since August 2022 have been treated with 2-fraction spine SBRT. Most patients were treated at 1 (45%) or 2 (40%) spinal levels, with the thoracic (55%) and lumbar (50%) spine being the most common locations. Common primary sites included the lung (30%), breast (20%), esophagus (15%), and prostate (10%). The rate of local control was 100%, while the rate of vertebral compression fracture was 15%. No esophageal or bowel toxicity occurred, and no fractures required intervention. Conclusions: These findings suggest that 2-fraction spine SBRT is safe and effective, consistent with existing Level I evidence. Our local control rate exceeding 95% aligns with the literature, indicating the feasibility and achievability of implementing this approach in the United States over a short period of time.