Cost-effectiveness analysis of enzalutamide for patients with chemotherapy-naive metastatic castration-resistant prostate cancer in Japan

Background: We aimed to evaluate cost-effectiveness of enzalutamide in chemotherapy-naive metastatic castration-resistant prostate cancer patients in Japan. Methods: A Markov model was developed to capture time spent by patients in various health states: stable, progression and death. Abiraterone acetate and docetaxel were set as active comparators. Clinical outcomes were obtained from the PREVAIL, COU-AA-302 and TAX327 trials. Treatment sequence, concomitant drugs and therapies for adverse events were estimated from responses to a survey by 14 Japanese prostate cancer experts. The analytic perspective was public healthcare payer, with a 10-year time horizon. The incremental cost-effectiveness ratio was estimated from quality-adjusted life-years and Japanese public healthcare costs. Probabilistic sensitivity analysis was performed to assess the robustness of the findings. Results: According to the survey, the most common treatment sequences were (i) enzalutamide -> docetaxel -> cabazitaxel (enzalutamide-first sequencing), (ii) abiraterone -> enzalutamide -> docetaxel (abiraterone-first sequencing) and (iii) docetaxel -> enzalutamide -> cabazitaxel (docetaxel-first sequencing). In the base-case analysis, enzalutamide-first sequencing saved 1.74 million Japanese Yen versus abiraterone-first sequencing, with a 0.129 quality-adjusted life-year gain (dominant). Enzalutamide-first sequencing had a cost increase of 4.44 million Japanese Yen over docetaxel-first sequencing, with a 0.371 quality-adjusted life-years gain. The incremental cost-effectiveness ratio of enzalutamide-first sequencing versus docetaxel-first sequencing was estimated as 11.94 million Japanese Yen/quality-adjusted life-years. Probabilistic sensitivity analyses demonstrated that, compared with abiraterone-first sequencing, enzalutamide-first sequencing had an 87.4% probability of being dominant. Conclusions: Results modeled herein suggest that the enzalutamide-first sequencing is more cost-effective than the abiraterone-first sequencing, but less cost-effective than docetaxel-first sequencing for chemotherapy-naive patients with metastatic castration-resistant prostate cancer.