Radiosurgery for Benign Tumors of the Spine: Clinical Experience and Current Trends

In distinction to the development of the clinical indications for intracranial radiosurgery, spine radiosurgery's initial primary focus was and still remains the treatment of malignant disease. The role of stereotactic radiosurgery for the treatment of intracranial benign tumors has been well established. However, there is much less experience and much more controversy regarding the use of radiosurgery for the treatment of benign tumors of the spine. This study presents the clinical experience and current trends of radiosurgery in the treatment paradigm of benign tumors of the spine as part of a dedicated spine radiosurgery program. Forty consecutive benign spine tumors were treated using cone beam computed tomography (CBCT) image guidance technology for target localization. Lesion location included 13 cervical, 9 thoracic, 11 lumbar, and 7 sacral tumors. Thirty-four cases (85%) were intradural. The most common tumor histologies were schwannoma (15 cases), neurofibroma (7 cases), and meningioma (8 cases). Eighteen cases (45%) had previously undergone open surgical resection, and 4 lesions (10%) had previously been treated with conventional fractionated external beam irradiation techniques. This cohort was compared to a prior institutional experience of 73 consecutive benign spine tumors treated with radiosurgery. No subacute or long term spinal cord or cauda equina toxicity occurred during the follow-up period (median 26 months). Radiosurgery was used as the primary treatment modality in 22 cases (55%) and for recurrence after prior open surgical resection in 18 cases (45%). The mean prescribed dose to the gross tumor volume (GTV) was 14 Gy (range 11 to 17) delivered in a single fraction in 35 cases. In 5 cases in which the tumor was found to be intimately associated with the spinal cord with distortion of the spinal cord itself, the prescribed dose to the GTV was 18 to 21 Gy delivered in 3 fractions. The GTV ranged from 0.37 to 94.5 cm³ (mean 13.2 cm³, median 5.1 cm³). No evidence of tumor growth was seen on serial imaging in any case. Compared to the prior cohort, there was a trend towards increased patient age, GTV, and use of radiosurgery in the post-surgical setting, as well as a simultaneous decrease in the prescription dose. Radiosurgery is a safe and clinically effective treatment alternative for benign spinal neoplasms. While surgical extirpation is currently felt to be the best initial treatment option for most benign spinal tumors, spine radiosurgery has been demonstrated to have long-term clinical and radiographic benefit for the treatment of such lesions. In a similar manner in which spine radiosurgery has become a primary treatment option for a variety of intracranial benign tumors, radiosurgery may become the most favorable treatment alternative for similar histologies when found in the spine. The application of radiosurgery for non-neoplastic spine disease deserves future investigation.