[Exploratory Analysis Results from Post-marketing Surveillance Study of Radium-223 in Japanese Patients with Castration-resistant Prostate Cancer and Bone Metastases: Subgroup Analysis by Age].

Objective: To perform an exploratory analysis on the safety and effectiveness of radium-223 (Ra-223) by patient baseline age, using the results of a post-marketing surveillance study of Ra-223 in castration-resistant prostate cancer patients with bone metastasis in Japan.

Method: The safety analysis population of 296 patients was stratified into two groups based on age (<75 and ≥ 75 years-old [yo]), and their characteristics, drugrelated treatment-emergent adverse events (TEAEs), and clinical laboratory values were evaluated. Additionally, these endpoints were evaluated in patients aged ≥ 80 yo.

Results: There were 148 patients in each of the <75-yo and ≥ 75-yo age groups, and 69 patients in the ≥ 80-yo age group. The characteristics of patients in the <75-yo group were suggestive of more aggressive disease at diagnosis of prostate cancer and a greater proportion of patients had prior chemotherapy compared with patients in the ≥ 75-yo age group. The incidences of overall drugrelated TEAEs and drug-related hematological TEAEs were slightly higher in the <75-yo age group; however, there was little difference in the incidences of drug-related TEAEs leading to drug discontinuation (1.4-4.1%) between patient groups. Changes in total alkaline phosphatase and prostate-specific antigen values were similar in all groups.

Conclusions: Ra-223 therapy seemed tolerable regardless of age in real-world practice in Japan. Especially, there were no new safety concerns of Ra-223 in elderly patients.