Clinical assessment of stereotactic IGRT: spinal radiosurgery

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 because of the availability of effective target immobilization devices. Recent advances in stereotactic IGRT have allowed for spinal applications. Large clinical experience with spinal radiosurgery to properly assess clinical outcomes has previously been limited. At our institution, we have developed a successful multidisciplinary spinal radiosurgery program in which 542 spinal lesions (486 malignant and 56 benign lesions) were treated with a single-fraction radiosurgery technique. Patient ages ranged from 18 to 85 years (mean 56 years). Lesion location included 92 cervical, 234 thoracic, 130 lumbar, and 86 sacral. The most common metastatic tumors were renal cell (89 cases), breast (74 cases), and lung (71 cases). The most common benign tumors were neurofibroma (24 cases), schwannoma (13 cases), and meningioma (7 cases). Eighty-nine cervical lesions were treated using skull tracking. Thoracic, lumbar, and sacral tumors were tracked relative to either gold or stainless steel fiducial markers. The maximum intratumoral dose ranged from 12.5 to 30 Gy (mean 20 Gy). Tumor volume ranged from 0.16 to 298 mL (mean 47 mL). Three hundred thirty-seven lesions had received prior external beam irradiation with spinal cord doses precluding further conventional irradiation. The primary indication for radiosurgery was pain in 326 cases, as a primary treatment modality in 70 cases, for tumor radiographic tumor progression in 65 cases, for post-surgical treatment in 38 cases, for progressive neurological deficit in 35 cases, and as a radiation boost in 8 cases. Follow-up period was at least 3 to 49 months. Axial and/or radicular pain improved in 300 of 326 cases (92%). Long-term tumor control was demonstrated in 90% of lesions treated with radiosurgery as a primary treatment modality and in 88% of lesions treated for radiographic tumor progression. Thirty of 35 patients (85%) with progressive neurological deficits experienced at least some improvement after treatment. Spinal stereotactic radiosurgery is now a feasible, safe, and clinically effective technique for the treatment of a variety of spinal lesions. The potential benefits of radiosurgical ablation of spinal lesions are short treatment time in an outpatient setting with essentially no recovery time and excellent symptomatic response. This technique offers a new therapeutic modality for the primary treatment of a variety of spinal lesions, including the treatment of neoplasms in medically inoperable patients, previously irradiated sites, for lesions not amenable to open surgical techniques, and as an adjunct to surgery.