Analyses based on number needed to treat benefit (NNTB) show that the overall survival (OS) benefit is similar when using abiraterone acetate (ZYTIGA), enzalutamide (XTANDI), or sipuleucel-T (Provenge) to treat men with chemotherapy-naïve metastatic castration-resistant prostate cancer (mCRPC). The data, however, favor sipuleucel-T for having the lowest direct cost.
“There is no question that all three treatments for mCRPC are expensive and that sipuleucel-T carries the highest initial cost. However, the estimated total drug cost to achieve an additional patient OS benefit declines over time with sipuleucel-T whereas it increases for the oral drugs that are given as ongoing therapy,” said David Morris, MD, a urologist with Urology Associates, Nashville, TN, who presented the research at the AUA annual meeting in Chicago.
“NNTB represents the expected number of patients needed to be treated to prevent one additional death compared to placebo at a specified time point, and it is a useful and intuitive measure of OS that can be included in the shared decision-making process about initial treatment options for mCRPC,” Dr. Morris said. “Ultimately, treatment decisions should be individualized, taking into account side effect profiles, the physician’s experience, and the patient’s characteristics and preferences.”
The analyses were performed using data from placebo-controlled pivotal trials investigating each of the treatments in men with chemotherapy-naïve mCRPC (COU-AA-302 for abiraterone, IMPACT for sipuleucel-T, and PREVAIL for enzalutamide). The NNTB values, which are calculated as the inverse of the absolute risk reduction, were derived from the studies’ Kaplan-Meier OS curves.
Costs for the oral drugs were taken from the 2019 Wholesale Acquisition Cost listed in the IBM Micromedex Red Book. The sipuleucel-T cost was based on the second quarter 2019 Medicare Part B payment and included both the leukapheresis and preparatory procedures needed for product manufacture.
For each of the oral drugs, the total drug cost at 24 months was calculated as the mathematical product of the monthly cost and its median treatment duration in the pivotal trial. For sipuleucel-T, the 24-month cost was based on the initial cost divided by 24 months. Cost per NNTB was calculated as the mathematical product of the drug cost, each NNTB value, and the duration of treatment.
The results showed that sipuleucel-T had the shortest median duration of treatment (1 month) followed by abiraterone (13.8 months) and enzalutamide (16.6 months). Cost of median duration of treatment for sipuleucel-T, abiraterone, and enzalutamide was approximately $133,000, $150,000, and $192,000, respectively.
The NNTB at 24 months was 10 for sipuleucel-T, 16 for abiraterone acetate, and 12 for enzalutamide, and the cost per NNTB for the three treatments was approximately $665,000, $2.4 million, and $2.3 million, respectively.
An NNTB calculation was also done for African-American men treated with sipuleucel-T with a result of 3 at 24 months.
“Survival outcomes for the subgroup of African-American men were not reported in the abiraterone and enzalutamide clinical trials. The NNTB values for sipuleucel-T show that its OS benefit was greater in African-American men than in the overall IMPACT population and suggest it is an effective therapy in African-American men,” said Dr. Morris.