Treatment of spinal neoplasms using frameless stereotactic radiosurgery

Abstract

Purpose of study: The use of stereotactic radiosurgery for the treatment of spinal lesions has been limited by the availability of effective target immobilization devices. Thi≈s study evaluated the feasibility of treating spinal neoplasms with a single-fraction radiosurgical technique using the CyberKnife Image-Guided Radiosurgery System. During treatment, a real-time image-guidance system tracks the patient's tumor. Information about tumor position is communicated to a robotic arm that aims the radiation-generating linear accelerator.Methods used: Nineteen consecutive patients with spinal neoplasms were treated. The location in the spine included 14 cervical, 2 thoracic and 3 lumbar. Fourteen lesions were metastatic, and five were primary. Cervical lesions were tracked relative to the skull; lower spinal lesions were tracked relative to percutaneously placed fiducial markers. Tumor volume ranged from 0.8 to 74.9 cc (mean, 17.1 cc). Fourteen lesions had received prior external beam irradiation. Dose plans were calculated based on computed tomography images acquired using 1- to 3-mm slices. Each plan was tested using a phantom to assure 1-mm accuracy. Tumor dose was maintained at 12 to 14 Gy to the 80% isodose line; spinal cord volume receiving greater than 8 Gy ranged from 0.0 to 1.4 cc (mean, .35 cc).of findings: All patients tolerated the procedure in an outpatient setting. No acute radiation toxicity or new neurological deficits occurred. One patient had a transient flare of neck pain. Axial and radicular pain improved in all patients who were symptomatic before treatment.Relationship between findings and existing knowledge: This study describes the largest series using a revolutionary therapeutic modality for the treatment of spinal neoplasms.Overall significance of findings: Spinal stereotactic radiosurgery using a frameless image-guided system was found to be safe and accurate. The major potential benefits of radiosurgical ablation of spinal neoplasms are short treatment time in an outpatient setting with rapid recovery time and good palliative effect. This device offers an alternative therapeutic modality for the treatment of metastatic lesions in medically inoperable patients, previously irradiated sites and for lesions not amenable to open surgical techniques or as an adjunct to surgery. Studies are currently underway to assess the efficacy of this novel treatment.Disclosures: Device or drug: CyberKnife Image-Guided Radiosurgery System. Status: approved.Conflict of interest: Peter C. Gerszten, speaker's bureau for Accuracy Inc. (Sunnyvale, CA.)