Preliminary clinical experience with linear accelerator-based spinal stereotactic radiosurgery

A prototype device called an extracranial stereotactic radiosurgery frame was used to deliver stereotactic radiosurgery, with a modified linear accelerator, to metastatic neoplasms in the cervical, thoracic, and lumbar regions in five patients. In all patients, the neoplasms had failed to respond to spinal cord tolerance doses delivered by standard external fractionated radiation therapy to a median dose of 45 Gy (range, 33-65 Gy/11-30 fractions). The tumors were treated with single-fraction stereotactic radiosurgery with the spinal stereotactic frame for immobilization, localization, and treatment. The median number of isocenters was one (range, one to five) with a median single fraction dose of 10 Gy (range, 8-10 Gy) with median normalization to 80% isodose contour (range, 80-160%). There has been a single complication of esophagitis to date from radiosurgery of a tumor involving the C6-T1 segments; the esophagitis resolved with medical therapy. Median follow-up in this group of patients has been 6 months (range, 1-12 mo). To date, there has been no radiographic or clinical progression of the treated tumor in any patient. Two patients have died from systemic metastatic disease. In the three surviving patients, there has been computed tomographic- or magnetic resonance-documented regression of the treated tumor with a decrease of thecal sac compression with a median follow-up of 6 months (range, 3-14 mo). These five patients represent the first clinical application of stereotactic radiosurgery in the spine. The results suggest that extracranial radiosurgery may be suitable for the treatment of paraspinal neoplasms after external fractionated radiation therapy, even in the face of spinal cord compression.