Technique for stereotactic body radiotherapy for spinal metastases

Stereotactic body radiotherapy (SBRT) is an emerging technique for spinal tumours that is a natural succession to brain radiosurgery. The spine is an ideal site for SBRT due to its relative immobility and the potential clinical benefits of high dose delivery, particularly to optimise local control and avoid disease progression that can result in spinal cord compression. However, the proximity of the tumour to the spinal cord, with the potential for radiation myelopathy if the dose is delivered inaccurately or if the spinal cord dose limit is set too high, demands technical accuracy with radiation myelopathy a feared complication. Spine SBRT has been delivered with either a robotic-based linac system such as the Cyberknife, or with linac-based systems equipped with a multileaf collimator and image guidance system. Regardless of the technology, spine SBRT demands sophisticated treatment planning and delivery. This case-based technical review outlines the SBRT apparatus, planning and treatment delivery in use at the University of Toronto, Toronto, Canada.