Appropriate endpoints for stereotactic body radiotherapy for bone metastasis: Classification into five treatment groups

Treatment of bone metastasis using stereotactic body radiotherapy (SBRT) is being widely used in clinical practice. The reported clinical advantages of SBRT include high pain and local control rates, high response rates against bone metastasis from radio-resistant tumors, and safe re-irradiations. Although most reports in the literature use local control as the primary treatment endpoint, this endpoint is not appropriate because local control does not relate directly to patient benefit. Herein, we proposed five pathophysiology-based patient groups, as well as appropriate endpoints for each group.