Outcomes of Spine Stereotactic Body Radiation Therapy in Patients Previously Treated With Conventional Radiation

Abstract

Spine stereotactic body radiation therapy (sSBRT) is used to treat relapse following conventional radiation (cEBRT). This study seeks to determine the risk factors for local relapse both radiographically and in regards to pain. Patients who underwent sSBRT following cEBRT were included in an IRB-approved database. RPA Class, histology, presence of paraspinal disease, multilevel disease (more than 1 spinal level involved), presence of epidural disease, neural foramina involvement, and dosimetric factors (volume, prescription dose, % coverage by the prescription dose, maximum dose, minimum dose) were retrospectively collected. These factors were correlated to radiographic control and pain progression as determined by the Brief Pain Inventory. A total of 79 procedures were performed in 65 patients. Median age was 60 years (range: 27-90). Median follow-up was 8.5 months (range: 0-57.7) and median overall survival was 10.5 months. Median prescription dose was 14 Gy (range: 8-25) typically over 1 fraction (range: 1-10). At presentation, 10.1% were asymptomatic, 6.3% had neurological deficits, 72.2% had pain, and 11.4% had pain and neurological deficits. Following sSBRT, pain control was seen in 81% and 78.5% had radiographic control at last follow-up. Median time to pain relief was 0.7 months (range: 0-3.9). RPA Class, histology, presence of paraspinal disease, multilevel disease, presence of epidural disease, and neural foramina involvement did not predict for radiographic control or pain progression. None of the dosimetric factors predicted for radiographic control or pain progression as well. None of the patients in this series developed myelopathy. New vertebral body fracture developed in 8.9% of treatments. sSBRT for progression post cEBRT is effective and safe. Pain relief is quick following sSBRT. Our current standard dose is 16 Gy in 1 fraction. These results are consistent with our data for patients treated upfront for spine metastases. Previous cEBRT does not appear to compromise the effectiveness of sSBRT.