Administration of radium‐223 and the prognosis in Japanese bone metastatic castration‐resistant prostate cancer patients: A large database study

BACKGROUND: The ALSYMPCA trial revealed radium‐223 (Ra‐223) to be a life‐prolonging agent for bone metastatic castration‐resistant prostate cancer (CRPC). However, only 2.8% of enrolled patients in that clinical trial were Asian, and no Japanese patients were enrolled. Several retrospective studies have been published concerning Japanese bone metastatic CRPC patients receiving Ra‐223. However, no study has yet reported the correlation between Ra‐223 induction and the survival in Japanese bone metastatic CRPC patients. This study investigated the effect of Ra‐223 as a life‐prolonging agent in a large Japanese healthcare fee database. METHODS: A total of around 410 000 prostate cancer patients were extracted from this database, and 25 934 were diagnosed with CRPC. In these patients, the age, date of the CRPC diagnosis, date of Ra‐223 induction, and prognosis were analyzed. RESULTS: A total of 1628 patients received Ra‐223, and 6693 patients were diagnosed with bone metastasis CRPC, with the remaining 17 613 patients diagnosed with CRPC without bone metastasis. The patients who completed six courses of Ra‐223 showed a significantly more favorable overall and cancer‐specific survival than those who received ≤5 courses (p < 0.0001 and p < 0.0001, respectively). For time from CRPC diagnosis date to death, the Ra‐223 induction group showed a significantly more favorable prognosis with regard to both the overall and cancer‐specific survival than the bone metastatic CRPC patients without Ra‐223 (p < 0.0001 and p < 0.0001, respectively). CONCLUSIONS: Bone metastatic CRPC patients who received Ra‐223 showed a significantly better prognosis than bone metastatic CPRC patients who did not receive Ra‐223.