The era of stereotactic body radiotherapy for spinal metastases and the multidisciplinary management of complex cases

Spinal metastases are increasingly becoming a focus of attention with respect to treating with locally "ablative" intent, as opposed to locally "palliative" intent. This is due to increasing survival rates among patients with metastatic disease, early detection as a result of increasing availability of spinal MRI, the recognition of the oligometastatic state as a distinct sub-group of favorable metastatic patients and the advent of stereotactic body radiotherapy (SBRT). Although conventionally fractionated radiation therapy has been utilized for decades, the rates of complete pain relief and local control for complex tumors are sub-optimal. SBRT has the advantage of delivering high total doses in few fractions (typically, 24 Gy in 1 or 2 fractions to 30-45 Gy in 5 fractions) that can be considered "ablative". With mature clinical experience emerging among early adopters, we are realizing beyond efficacy the limitations of spine SBRT. In particular, toxicities such as vertebral compression fracture, and epidural disease progression as the most common pattern of local tumor progression. As a result, the multidisciplinary evaluation of cases prior to SBRT is emphasized with the intent to identify patients who could benefit from surgical stabilization or down-staging of epidural disease. The purpose of this review is to provide an overview of the current literature with respect to outcomes, technical details for safe delivery, patient selection criteria, common and uncommon side effects of therapy, and the increasing use of minimally invasive surgical techniques that can improve both safety and local control.