CyberKnife radiosurgery for spinal neoplasms

Abstract

The role of stereotactic radiosurgery for the treatment of intracranial lesions is well established. Its use for the treatment of spinal lesions has been limited by the availability of effective target immobilization and localization technologies. Conventional external beam radiotherapy lacks the precision to allow delivery of large doses of radiation near radiosensitive structures such as the spinal cord. The CyberKnife (Accuray Inc., Sunnyvale, Calif., USA) is an imageguided frameless stereotactic radiosurgery system that allows for the radiosurgical treatment of spinal lesions. The system utilizes the coupling of an orthogonal pair of X-ray cameras to a dynamically manipulated robot-mounted lightweight linear accelerator which has 6 d.f. that guides the therapy beam to the intended target without the use of frame-based fixation. Realtime imaging tracking allows for patient movement tracking with 1mm spatial accuracy. Cervical spine lesions are located and tracked relative to skull bony landmarks; lower spinal lesions are tracked relative to percutaneously placed gold fiducial bone markers. Spinal stereotactic radiosurgery using a frameless image-guided system is now both feasible and safe. The major potential benefits of radiosurgical ablation of spinal lesions are short treatment time in an outpatient setting with rapid recovery and good symptomatic response. This technique offers a successful therapeutic modality for the treatment of a variety of spinal lesions as a primary treatment or for lesions not amenable to open surgical techniques, in medically inoperable patients, lesions located in previously irradiated sites, or as an adjunct to surgery.