Number needed to treat and associated incremental costs of treatment with enzalutamide versus abiraterone acetate plus prednisone in chemotherapy-naive patients with metastatic castration-resistant prostate cancer

Objective: Enzalutamide (ENZA) and abiraterone acetate plus prednisone (AA) are approved second-generation hormone therapies for chemotherapy-naive metastatic castration-resistant prostate cancer (mCRPC). This study compared ENZA with AA in chemotherapy-naive mCRPC by calculating the number needed to treat (NNT) and associated incremental costs to achieve one additional chemotherapy-naive patient with mCRPC free of radiographic progression, chemotherapy, or death over a 1-year time horizon. Methods: Clinical outcomes were obtained from the PREVAIL and COU-AA-302 trials. Three outcomes were evaluated: radiographic progression-free survival, time to cytotoxic chemotherapy initiation, and overall survival at 1 year. NNT was calculated as the reciprocal of the outcome event rate difference for ENZA compared with AA. The incremental costs to achieve one additional outcome at 1 year were calculated as the difference in cost per treated patient multiplied by the NNT. Per-treated-patient costs were considered from a US payer perspective and included medications, monitoring, adverse events, post-progression treatments, and end-of-life care. Results: Within a 1-year time horizon, the total cost per treated patient for ENZA was $2,666 less than AA. Compared with AA, treating 14 patients with ENZA resulted in one additional patient free of progression or death over 1 year; treating 26 patients with ENZA resulted in one additional patient with chemotherapy delayed over 1 year; and treating 91 patients with ENZA resulted in one additional patient free of death over 1 year. Therefore, ENZA is cost-effective compared with AA for all three outcomes evaluated, and the modeled results suggest ENZA is associated with potentially improved clinical outcomes in delaying chemotherapy initiation and disease progression for chemotherapy-naive patients. The results are robust in sensitivity analyses, where the effect of changes in key model inputs and assumptions were tested. Conclusion: The results modeled in the present study suggest ENZA is cost-effective compared with AA for treating chemotherapy-naive patients with mCRPC.