COST EFFECTIVENESS OF DABIGATRAN, APIXABAN, RIVAROXABAN, EDOXABAN AND WARFARIN FOR ISCHEMIC STROKE PROPHYLAXIS AMONG PATIENTS WITH ATRIAL FIBRILLATION: US PRIVATE PAYER'S PERSPECTIVE

Purpose:

   To compare the cost effectiveness of dabigatran 150mg, rivaroxaban 20mg, apixaban 5mg, edoxaban 60mg and dose-adjusted warfarin therapy among patients with atrial fibrillation (AF). 

Method:    

   A Markov model was constructed to project the lifetime costs and quality adjusted survival (QALYs) of oral anticoagulants using a private payer’s perspective. The distribution of stroke risk (CHADS2) and age of the modeled population was derived from a cohort of commercially insured patients with new-onset AF (mean age = 65.01 and CHADS2 score ≥ 1).  Probabilities of treatment specific events were derived from published trials (ARISTOTLE, ROCKET, RELY, and ENGAGE).  Event and downstream costs were determined from cost of illness studies. Average wholesale prices for the drugs were obtained from 2015 Medispan data. Structural and probabilistic sensitivity analyses were performed by varying event and follow-up costs and generating 100 cohorts of 1000 patients. Subgroup analyses among patients above and below the age of 65 were also conducted. 

Result:

   In the base case analysis, warfarin was the least costly ($43,720) followed by edoxaban ($61,708), dabigatran ($63,972), apixaban ($64,365) and rivaroxaban ($65,473). Apixaban had the highest QALYs gained (9.37), followed by dabigatran (9.31), edoxaban (9.29), rivaroxaban (9.20) and warfarin (8.97). None of the newer oral anticoagulants were found to be cost effective over warfarin. In order to become the preferred strategies at a willingness to pay threshold of $50000/QALY, monthly drug costs would have to be reduced by $3, $14, $19, and $109 for apixaban, edoxaban, dabigatran, and rivaroxaban respectively. In the probabilistic sensitivity analysis, warfarin was were preferred strategy in 59% of the iterations. In the structural sensitivity analyses, dabigatran and apixaban were cost effective 50% and 26% of the times. In the subgroup analysis among patients ≥ 65 years of age, apixaban, dabigatran and edoxaban were cost effective compared to warfarin with apixaban dominating other novel anticoagulants (NOACs). Among patients <65 years of age none of the NOACs were cost effective at a WTP of $50,000/QALY.

Conclusion:

   The quality adjusted survival between all NOACs is similar; however, apixaban is the most effective and among the elderly (≥ 65) had an incremental cost-effectiveness ratio (ICER) representing high value as compared to warfarin. Given the similarity between QALYs of all NOACs, the model findings were highly sensitive to drug prices.