Spinal SBRT for Spine Metastases

Bone metastases frequently involve the spine and can cause significant morbidity with pain and neurologic compromise. A shift toward hypofractionated radiotherapy delivered over 1 to 5 fractions has taken place to provide increased long-term local control and pain relief. Patients with radioresistant histologies, painful metastases, oligometastatic disease, and/or patients who have had previous radiotherapy to the region, should be considered for spine stereotactic body radiotherapy (SBRT). Evaluation at presentation includes an assessment of spine stability and the extent of epidural disease. Potentially unstable or frankly unstable metastases and high-grade epidural disease should have a spine surgical consult prior to SBRT. If surgery is needed, SBRT can be delivered in the post-operative setting. Spine SBRT is performed with the patient immobilized in a near rigid body immobilization device, simulation with thin-slice computed tomography (CT) and volumetric thin-slice axial T1 and T2 magnetic resonance (MR) images for subsequent image fusion, and delivery with an image-guided linac delivery apparatus. Guidelines for patient selection and contouring are well described, and organ-at-risk constraints from both evidence-based toxicity analyses and multi-center randomized controlled trials are available. Patients need to be followed closely with spine MRI for tumor progression, pseudoprogression, and side effects of radiotherapy, which can include vertebral compression fracture.