NEW THERAPEUTIC OPTIONS IN METASTATIC CASTRATION-RESISTANT PROSTATE CANCER (MCRPC): CAN COST-EFFECTIVENESS ANALYSIS HELP IN TREATMENT DECISION?

Purpose:  Since 2010, three new drug treatments have been approved for metastatic castration-resistant prostate cancer (mCRPC) in patients who fail docetaxel therapy.  We evaluated the cost-effectiveness of abiraterone, cabazitaxel, and enzalutamide compared to placebo for mCRPC.

Method:  A decision-tree model was constructed comparing the three treatment options for mCRPC patients over an 18 month period from a societal perspective in 2012 USD.  Chance nodes included baseline pain as a severity indicator, significant adverse effects (neutropenia, cardiac events, or seizures), and survival at 18 months.  Probabilities, survival rates and health utilities were extracted from clinical trials (COU-AA, TROPIC and AFFIRM) and other published studies.  Model cost inputs included drug treatment and administration, side-effect management and prevention, radiation for pain, and death associated costs.  Life expectancies were extrapolated using the DEALE declining exponential function. Adjustments were made to the survival curves for the enzalutamide branch to account for higher baseline placebo survival rates in clinical trial data relative to abiraterone and cabazitaxel trials. Probabilistic sensitivity analyses, acceptability curve and net benefit calculations were performed.

Result:  Abiraterone was the most cost-effective of the treatments ($123,430/QALY) compared to placebo, enzalutamide was $437,623/QALY compared to abiraterone, and cabazitaxel was $351,865/QALY compared enzalutamide.   Enzalutamide and cabazitaxel were not cost-effective compared to placebo at $154,349/QALY and $163,177/QALY, respectively.  Acceptability curves showed abiraterone was cost-effective 29.3% of the time with a willingness to pay (WTP) threshold of $100,000. At this threshold, enzalutamide and cabaxitaxel were cost-effective 20.9% and 16.1% of the time, respectively. The model was sensitive to changes in cost of the drugs, life expectancy and survival rate.  Sensitivity analysis shows that enzalutamide will become the most cost-effective option if the price of the medication decreased by 26% and other drug costs remained the same.

Conclusion:  Based on the cost-effective analysis, we would recommend abiraterone for treatment of mCRPC despite not quite falling under the usually accepted WTP threshold.  Further analysis should examine comparative survival across the three drugs.