RADT-29. SINGLE INSTITUTION EXPERIENCE OF IMMEDIATE POSTOPERATIVE SPINE SBRT AND INITIATION OF A PHASE 2 STUDY WITH SAFETY PILOT LEAD-IN

Abstract The standard of care for managing spinal column metastases with epidural cord compression or unstable fracture is surgery followed by conventional radiotherapy or stereotactic body radiotherapy (SBRT) about 4 weeks postoperatively. This approach is prone to delays, which can compromise oncologic outcomes and limit access to care for some patients. Delivering postoperative spine SBRT sooner after surgery, prior to hospital discharge, may improve access to care and initiation of systemic therapy without increasing wound complications. We retrospectively reviewed six patients who underwent expedited postoperative spine SBRT. Three patients underwent open surgeries; three had minimally invasive procedures. Spine SBRT was initiated at a median of 8+/-3 days postoperatively. The radiotherapy regimen was 30Gy/5fx for three patients, 18Gy/1fx for two patients, and 20Gy/1fx for one patient. In equivalent dose in 2Gy fractions (EQD2), the median average regional spinal cord dose was 13.5+/-10.7Gy; the median max (0.3cc) spinal cord dose was 27.9+/-12.0Gy; the median max (0.3cc) skin dose was 19.9+/-9.0Gy. One patient experienced low-grade, superficial wound dehiscence within the month following treatment, which healed without any intervention. Based on this experience, we initiated a trial investigating the safety and efficacy of expedited postoperative spine SBRT. This is a single-site, single-arm phase 2 trial with a safety pilot lead-in. Adults with spine metastases involving at most 2 contiguous levels and no prior radiation within the anticipated treatment field are eligible. Postoperative SBRT will be initiated within 7 days of surgery with expedited postoperative MRI, CT simulation, and treatment planning. Prescription doses recommended by consensus guidelines (16-40Gy/1-5fx) will be allowed. Stratification includes surgical approach, extent of resection, and hardware material. The co-primary endpoints are wound complication rate by CDC criteria at 1 month and local control rate by MRI at 6 months, compared to historic institutional rates of 10.8% and 90%, respectively.