A randomized phase III trial was planned to commence in October 2017. Resectable giant cell tumor of bone (GCTB) without possible postoperative large bone defect has been treated by curettage with local adjuvant treatment, with the local recurrence rate found to be as high as 24.6-30.8%. The aim of this study is to confirm the superiority of preoperative denosumab for patients with GCTB without possible postoperative large bone defect. A total of 106 patients will be accrued from 34 Japanese institutions over 5 years. The primary endpoint is relapse-free survival (RFS). Secondary endpoints include overall survival, joint-preserved survival, local RFS, metastasis-free survival, adverse events, serious adverse events, surgical and postoperative complications, and discontinuation of denosumab. This trial is conducted by the Bone and Soft Tissue Tumor Study Group in the Japan Clinical Oncology Group and has been registered in the UMIN Clinical Trials Registry as UMIN000029451 [http://www.umin.ac.jp/ctr/index.htm].