Image-guided hypo-fractionated stereotactic radiosurgery to spinal lesions

OBJECTIVE: This article demonstrates the technical feasibility of noninvasi ve treatment of unresectable spinal vascular malformations and primary and metastatic spinal tumors by use of image-guided frameless stereotactic radi osurgery. METHODS: Stereotactic radiosurgery delivers a high dose of radiation to a t umor volume or vascular malformation in a limited number of fractions and m inimizes the dose to adjacent normal structures. Frameless image-guided rad iosurgery was developed by coupling an orthogonal pair of x-ray cameras to a dynamically manipulated robot-mounted linear accelerator that guides the therapy beam to treatment sites within the spine or spinal cord, in an outp atient setting, and without the use of frame-based fixation. The system rel ies on skeletal landmarks or implanted fiducial markers to locate treatment targets. Sixteen patients with spinal lesions (hemangioblastomas, vascular malformations, metastatic carcinomas, schwannomas, a meningioma, and a cho rdoma) were treated with total treatment doses of 1100 to 2500 cGy in one t o five fractions by use of image-guided frameless radiosurgery with the Cyb erKnife system (Accuray, Inc., Sunnyvale, CA). Thirteen radiosurgery plans were analyzed for compliance with conventional radiation therapy. RESULTS: Tests demonstrated alignment of the treatment dose with the target volume within +/- 1 mm by use of spine fiducials and the CyberKnife treatm ent planning system. Tumor patients with at least 6 months of follow-up hav e demonstrated no progression of disease. Radiographic follow-up is pending for the remaining patients. To date, no patients have experienced complica tions as a result of the procedure. CONCLUSION: This experience demonstrates the feasibility of image-guided ro botic radiosurgery for previously untreatable spinal lesions.