A prospective multicentre feasibility study of stereotactic body radiotherapy in Japanese patients with spinal metastases

Objective Stereotactic body radiotherapy has emerged as an attractive alternative to conventional radiotherapy for spinal metastases. However, it has limitations, including the need for advanced techniques and specific adverse effects. The present trial aimed to validate the feasibility and safety of stereotactic body radiotherapy in Japanese patients with spinal metastases. Methods Patients with one or two spinal metastases received stereotactic body radiotherapy of 24 Gy in two fractions. The primary endpoint was the proportion of severe adverse effects (≥ grade 3) in patients within 6 months after spine stereotactic body radiotherapy. Adverse effects were evaluated according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 4. The treatment protocol was considered feasible and tolerable if the proportion of severe adverse effects was 10% or less. Results Overall, 20 spinal segments in 20 patients who registered between March 2014 and October 2015 were included. Minor and major deviations were observed in the planning of 2 and 0 cases, respectively. The treatment completion rate was 100%. The median follow-up after registration was 24.5 (range: 1-61) months. Although four patients experienced acute grade 2 adverse effects, no grade 3 or higher adverse effects were observed within 6 months after spine stereotactic body radiotherapy. Vertebral compression fractures were observed in two patients (14 and 16 months after stereotactic body radiotherapy). The local control and pain response rates at 6 months were 100 and 83%, respectively. Conclusion This study demonstrated the feasibility and safety of spine stereotactic body radiotherapy in Japanese patients with spinal metastases.