Strategies to Mitigate Toxicities From Stereotactic Body Radiation Therapy for Spine Metastases

Improvements in systemic therapy are translating into more patients living longer with metastatic disease. Bone is the most common site of metastasis, where spinal lesions can result in significant pain impacting quality of life and possible neurological dysfunction resulting in a decline in performance status. Stereotactic body radiation therapy (SBRT) of the spine has emerged as a promising technique to provide durable local control, palliation of symptoms, control of oligoprogressive sites of disease, and possibly augment the immune response. SBRT achieves this by delivering highly conformal radiation therapy to allow for dose escalation due to a steep dose gradient from the planning target volume to nearby critical organs at risk. In our review, we provide an in-depth review and expert commentary regarding seminal literature that defined clinically meaningful toxicity endpoints with actionable dosimetric limits and/or clinical management strategies to mitigate toxicity potentially attributable to SBRT of the spine. We placed a spotlight on radiation myelopathy (de novo, reirradiation after conventional external beam radiation therapy or salvage after an initial course of spinal SBRT), plexopathy, vertebral compression fracture, pain flare, esophageal toxicity, myositis, and safety regarding combination with concurrent targeted or immune therapies.