COST EFFECTIVENESS OF THERAPIES FOR CASTRATION RESISTANT METASTATIC PROSTATE CANCER

Purpose: Metastasis develops in 10% to 20% of patients with prostate cancer, resulting in reduced survival. The current treatment options for mCRPC include mitoxantrone, cabazitaxel, abiraterone and enzalutamide. The objective of our current study to evaluate the cost effectiveness of all these available therapies.

Method: A decision tree model was adopted from Zhong et al study and updated to compare the costs and quality adjusted survival of four available treatment options mCRPC versus a standard prednisolone regimen, using a 2015 payer’s perspective. The decision model included; baseline pain level as a measure for disease severity, development of treatment specific side effects and treatment specific survival.  Data on probabilities life expectancies and utilities were obtained from clinical trial data (COU-AA, AFFIRM, Tropic) and other published sources. The cost parameters were incorporated from the following categories: drug treatment, radiation therapy, therapy-specific side effects, and death. Incremental cost effectiveness ratios were calculated along with total cost and quality adjusted life years (QALYs). One way and probabilistic sensitivity analyses were conducted to explore the robustness of model findings.

Result: In the base case analysis, cabazitaxel therapy was the most expensive ($139978), followed by enzalutamide ($133,834), abiraterone while ($120,260), mitoxantrone ($93,255), prednisolone ($82,930). Quality adjusted life expectancy was highest with cabazitaxel (0.76 QALY), followed by abiraterone (0.70 QALY), mitoxantrone (0.58 QALY), enzalutamide (0.56 QALY) and prednisolone (0.43 QALY).  Mitoxantrone was found to be the most cost effective treatment ($51,524.53/QALYs) compared to prednisolone. When compared to mitoxantrone abiraterone and cabazitaxel have high incremental cost effectiveness ratios ($220,803/QALY and $353,203/QALY respectively) while enzalutamide was dominated. At a willingness to pay of $100,000/QALY, the cost effectiveness acceptability curves showed that mitoxantrone and abiraterone were cost effective 23.4% and 24.6% times respectively. One-way sensitivity analysis showed that abiraterone had an ICER below $100,000/QALY when the price of abiraterone reduced by 30.1%.

Conclusion: Treatment of mCRPC with recently developed therapies can extend the survival, however, the gains in survival are accompanied by significant costs with abiraterone, cabazitaxel and enzalutamide.  At 2015 prices, mitoxantrone which has a lower side effect profile appears would be cost effective at conventional willingness to pay thresholds.