[Insufficiency fracture of the sacrum after hormonal therapy and radiotherapy for prostate cancer: A case in which 99mTc-MDP bone scintigraphy was useful for differential diagnosis].

A case in which radiotherapy was requested for bone metastases from prostate carcinoma after hormonal and radiation therapy and diagnosed as insufficiency fracture of the sacrum on bone scan was reported. A 78-year-old man underwent endocrine therapy with luteinizing hormone releasing hormone agonists and radical radiotherapy toward pelvis for prostate cancer. The onset of buttock pain started from the nine-month after the beginning of radiotherapy, and was diagnosed as sacrum metastasis by MRI, and radiotherapy was requested again for pain control. However, on bone scan, butterfly-like changed accumulation was noted, therefore sacrum insufficiency fracture was suspected. Addition of CT inspection and reconfirmation of MRI were performed, and bone metastases became negative, and serial observation was performed of the painkilling effect after that. No tumor marker rise was seen after five months without sigh of new bone metastases and the final diagnosis became insufficient fracture. In order to avoid unnecessary treatment, we think that the view of bone scintigram for diagnosis of sacrum insufficient fracture should be known.