Determination of sample size
Because this study is a phase II exploratory clinical trial to evaluate endpoints, treatment methods, and target patient groups to be tested in a subsequent phase III trial, the target number of patients is 44 (including an anticipated 40 evaluable cases and four dropouts (10%)) based on the number of cases that can be accumulated during the study period (enrollment period: two years, observation period: two years). Assuming a median radiologic bone progression-free survival in the control and study treatment groups of six and 12 months, respectively (hazard ratio: 0.50), the power will be 54.7% with an allocation ratio of 1:1 and a two-sided significance level of 0.05. The target sample size would be achieved according to the number of cases we have treated to date.