A Prospective, Phase II Study Demonstrating the Potential Value and Limitation of Radiosurgery for Spine Metastases

Abstract

To evaluate toxicity, efficacy, feasibility, and target volume dosimetry of single-fraction stereotactic body radiotherapy or radiosurgery for spine tumors. Twenty-five patients were treated on a prospective phase II protocol of single-fraction stereotactic body radiotherapy or radiosurgery for tumors near the spinal cord (N = 21). Patients received 15 Gy, given a spinal cord limit of 12 Gy to 0.1 mL for patients with no prior spine radiotherapy (N = 9), and 5 Gy to 0.5 mL for patients with prior spine radiotherapy (N = 12). The primary endpoint was toxicity. The secondary endpoint was efficacy measured with a pain scale, 2 neurologic function scales, and magnetic resonance scans. Minor endpoints were feasibility and dose coverage. Acute toxicity was grade 1 to 2 dysphagia or nausea. There were no late toxicities. Three patients experienced radiographic evidence of vertebral body compression in field; 2 were asymptomatic and 1 was managed with vertebroplasty. One patient progressed at the radiosurgery site (local control, 95%); 43% experienced pain relief. Most patients died or developed progressive systemic disease soon after radiosurgery. One-year progression-free survival was 5% with 60% of patients dead by 1 year. Patients with the site of radiosurgery as their only site of disease also did poorly: 2-year progression-free survival ≈ 10% with half dead of cancer within 2 years. There were no problems planning and delivering spine radiosurgery with a 60-minute treatment slot. In patients with and without prior radiotherapy, we achieved our target-coverage goal in 91% and 95%, respectively. Radiosurgery is an excellent option for patients with symptomatic spine metastases in previously irradiated areas. In patients without previous irradiation, the biology of metastatic cancer limits spine radiosurgery's ability to improve outcome.