Single fraction spine stereotactic ablative body radiotherapy with volumetric modulated arc therapy.

This study investigated a single institution’s experience with volumetric modulated arc therapy (VMAT) directed stereotactic ablative body radiotherapy (SABR) for vertebral metastases. From 2010 to 2014, 95 lesions of spinal metastases in 73 patients were treated with SABR using VMAT. Clinical local control, pain level, and use of steroid medication were employed to evaluate treatment responses. The majority (79%) of patients were treated with a radiation dose of 20 Gy in a single fraction. However, when normal tissue constraints could not be achieved, the dose was reduced to 18 Gy (11%) or 16 Gy (8%) in 1 fraction. At the median follow up of 12.7 months (mean 18.0, range 1-56 months), clinical local control was 97% (92 out of 95). There was a mean 81% (median 100%, range 28-100%) decrease in subjective pain score. Seventy-seven percent of patients had a decrease in narcotic pain medication use. Pain was completely resolved at the treatment site for 69% (66/95) of patients. Prior to the SABR treatment, 33% (31/95) of patients had epidural extension of tumor. Among patients with epidural involvement, 45% (14/31) exhibited neurologic impairment prior to treatment. Twenty-three percent (7/31) experienced spinal cord compression. Prior to treatment, 34 patients experienced some form of neurologic impairment. Of these patients, 24% (8/34) experienced improved motor functioning; the remaining 76% (26/34) of patients’ neurological dysfunction were stable. Our results indicate the SABR regimen using VMAT technique is clinically effective in achieving clinical local control and palliation. This is the first publication reporting clinical outcomes of VMAT directed SABR.