A novel prediction model for the completion of six cycles of radium-223 treatment and survival in patients with metastatic castration-resistant prostate cancer.

PURPOSE: We evaluated the predictive factors for completion of all six cycles of radium-223 (Ra-223) treatment in patients with metastatic castration-resistant prostate cancer (mCRPC). We also developed a novel prediction model for Ra-223 treatment completion using these predictors. METHODS: We retrospectively reviewed data from 122 patients with mCRPC who were treated with Ra-223. The predictive factors for the completion of six cycles of Ra-223 treatment were evaluated. Statistically significant predictive factors were then used to develop a prediction model for treatment completion. Finally, using this prediction model, we classified the overall survival (OS) of the entire cohort into three groups. RESULTS: We identified three significant variables as the predictive factors for treatment completion: baseline alkaline phosphatase (ALP) level, baseline hemoglobin (Hb) level, and baseline pain. The three groups generated using the prediction model were: group 1 (patients with three predictive factors, i.e., ALP < median, Hb ≥ median, and no pain), group 2 (patients with one to two predictive factors), and group 3 (patients without any predictive factors). The treatment completion rates differed between the three groups significantly. Furthermore, the OS also differed among the groups significantly. CONCLUSION: Our study suggested that the baseline ALP level, baseline Hb level, and baseline pain were the predictive factors of completion of all six cycles of Ra-223 treatment in patients with mCRPC. Our prediction model consisting of these factors could predict not only the completion of Ra-223 treatment, but also the post-treatment survival. This model can thus be useful for selection of patients for Ra-223 treatment.

Prognosis and safety of radium-223 with concurrent abiraterone acetate or enzalutamide use for metastatic castration-resistant prostate cancer: Real-world data of Japanese patients.

Objectives: To evaluate the real-world data on the efficacy and safety of a combination therapy with radium-223 (Ra-223) and second-generation androgen-receptor targeting agents (ARTAs), including abiraterone acetate (ABI) and enzalutamide (ENZ), among Japanese patients with bone metastatic castration-resistant prostate cancer (CRPC). Patients and methods: We retrospectively reviewed 79 patients with bone metastatic CRPC who were treated with Ra-223. The number of patients with concurrent ARTA use was 24:17 receiving ABI and 7 receiving ENZ. We evaluated the overall survival (OS) according to ARTA use and compared the survival of patients treated with Ra-223 with or without ARTA using multivariate analysis. Results: The median survival in the entire cohort was 23.5 months. The patients receiving Ra-223 combined with ARTA showed a tendency of better OS than patients treated with Ra-223 alone, although no significant difference was observed (median OS, 26.5 vs 23.5 months; P = .115). A multivariate analysis showed that the extent of disease on bone scan (EOD) scores and pain at baseline were significant predictors of OS. The concurrent use of bone-modifying agents (BMAs) was not significant for favorable OS (P = .050). However, the concurrent use of second-generation ARTA was not a significant factor for OS. Regarding safety, a bone fracture occurred in only one (4.2%) of 24 patients treated with combined Ra-223 and ARTA therapy. Conclusion: Our real-world data analysis suggested that Ra-223 combined with a second-generation ARTA is well tolerated in Japanese patients. The EOD score and pain at baseline are significant prognostic factors for OS, but the concurrent use of second-generation ARTA has no influence on OS among men treated with Ra-223. The concurrent use of BMA yields a marginally favorable OS.