去勢抵抗性前立腺がんの骨転移に対する塩化ラジウム（Ra-223）による治療

Bone and calcium metabolism associated with malignancy. Treatment of radium-223 dichloride for bone metastasis in castration resistant prostate cancer patients.

　前立腺がんの骨転移は造骨性が多く，去勢抵抗性前立腺がん（CRPC）の末期になると約90％が骨転移を有し，骨痛や病的骨折などの症候性骨関連事象を呈する。α線放射線治療薬の塩化ラジウム-223（Ra-223）は，骨痛の軽減などQOLの改善とともに，骨治療薬として初めてCRPCの全生存期間延長を示した。有害事象として，貧血・好中球減少・血小板減少など血液毒性や，悪心・下痢・骨痛などの非血液毒性があるが，軽微であり忍容性は高い。化学療法前の新規ホルモン剤を投与中に前立腺特異抗原（PSA）上昇を来している時や骨痛などの症状が出てきた時が，Ra-223の６回投与完遂の至適タイミングである。

　In patients with castration resistant prostate cancer（CRPC）, the most frequent site of metastases is bone particularly with osteoblastic change, which accounts for 90％ at the late stage of CRPC and is accompanied by symptomatic skeletal symptoms（SSEs）such as bone pain or pathological fractures. Radium-223（Ra-223）dichloride emits α particles and has been proven to improve overall survival（OS）and QOL by reducing SSEs in metastatic CRPC patients. Although hemotoxic adverse events（AEs）of Ra-223 treatment including anemia, neutropenia and thrombocytopenia, and non-hemotoxic AEs including nausea, diarrhea and bone pain have been reported, they were mild and well tolerated. The completion of 6 injections of Ra-223 is important for prolonging OS. The optimal time of Ra-223 administration is recommended the duration when PSA is increasing regardless of abiraterone or enzalutamide treatment prior to chemotherapy.