COST EFFECTIVENESS ANALYSIS OF ENZALUTAMIDE, ABIRATERONE PLUS PREDNISONE AND CABAZITAXEL PLUS PREDINSONE FOR THE TREATMENT OF VISCERAL METASTATIC CASTRATION RESISTANT PROSTATE CANCER (MCRPC) AFTER DOCETAXEL THERAPY

Background: Prostate cancer is the second leading cause of death after lung cancer among men in the US. The America Cancer Society predicts 164,690 new cases and 29,430 prostate cancer deaths in 2018. Of those diagnosed with prostate cancer, about 10-20 % will develop castration-resistant prostate cancer (CRPC) within 5 years of diagnosis and 70 % of those cases will metastasize to mCRPC. In 2014, nearly US $13.4 billion was spent on prostate cancer in the US and expected to reach US $15.4 billion by 2020; making prostate cancer the fifth most costly cancer. Objective: To conduct a cost-effective analysis of enzalutamide, abiraterone plus prednisone and cabazitaxel plus prednisone for the treatment of visceral mCRPC postdocetaxel failure from a US healthcare payer perspective utilizing life-time horizon Markov model. These medications received highest National Comprehensive Cancer Network (NCCN) guideline recommendation to treat visceral mCRPC post-docetaxel failure. Methods: A pharmacoeconomic model was constructed using Microsoft Excel® supported by visual basic codes and macros functions to estimate the cost-effectiveness [cost per life year gained (LYG)] and cost-utility analyses [cost per quality adjusted life year (QALY)] of visceral mCRPC therapies from a US healthcare perspective. We included direct medical costs in the model expressed in 2018 US dollars. All model costs were adjusted for vi inflation through the medical consumer price index (MCPI) as per the 1 quarter of 2018 and future costs were discounted at 3 %, (i.e. drug costs, grade (≥3) adverse events that occurred at least in 5 % of visceral mCRPC patients, costs of physician follow up, needed blood and imaging investigations). We calculated overall survival (OS) and progression-free survival (PFS) transition probabilities for each of the alternatives (abiraterone plus prednisone, enzalutamide and cabazitaxel plus prednisone) from the Kaplan-Meier survival curves of phase III trials using a digitizing program (Webplotdigitizer). Incremental cost-effectiveness ratios (ICERs) [cost per life year gained (LYG)] and incremental cost-utility ratios (ICURs) [cost per quality adjusted life year (QALY)] were calculated. Probabilistic sensitivity analysis was conducted to assess the robustness of base-case analysis and provide cost-effectiveness acceptability curve at various willingness-to-pay thresholds. Results: Model results indicate (98.7 %) of patients who receive abiraterone acetate plus prednisone, (83.8 %) who receive cabazitaxel plus prednisone and (86.8 %) who receive enzalutamide are expected to die in 3 years. In 1.5 years’ time, patients who receive enzalutamide will have significantly higher rates (14.47 %) of PFS than cabazitaxel plus prednisone (0.27 %) and abiraterone acetate plus prednisone (0.51 %). Enzalutamide was found to be more effective (1.58 LYG and 0.79 QALY) compared to abiraterone plus prednisone (1.20 LYG and 0.58 QALY) and cabazitaxel plus prednisone (1.48 LYG and 0.56 QALY). Enzalutamide was also associated with lower total costs ($157,830) compared to abiraterone acetate plus prednisone ($235,853) and cabazitaxel plus prednisone ($496,756). Cabazitaxel plus prednisone had an ICER & ICUR of $931.7K/LYG and almost 13 million/QALY respectively when compared to the next lowest treatment, abiraterone acetate plus prednisone. Conclusion: Enzalutamide is cost-effective compared to abiraterone acetate plus prednisone and cabazitaxel plus prednisone from a US healthcare perspective. Abiraterone acetate plus prednisone is less effective and less costly compared to cabazitaxel plus prednisone.