WASHINGTON – Apixaban yields the great medical cost savings of the three novel oral anticoagulants available as alternatives to warfarin for stroke prevention in patients with nonvalvular atrial fibrillation, according to a new comparative analysis.
This analysis differed from prior cost savings studies, which relied upon relative risk reductions for stroke and major bleeding events obtained directly from the pivotal phase III clinical trials conducted for each of the novel oral anticoagulants (NOACs).
Instead, the new analysis used as the comparator arm real-world event rates in warfarin-treated patients in a large national health insurance claims database. This was done because of the high likelihood that event rates in warfarin-treated controls in the clinical trials may be considerably lower than in everyday practice, since the trials were carried out in a selected patient population, with exclusion of the elderly and others at higher risk of adverse events, Michael Stokes explained at the annual meeting of the American College of Cardiology.
Michael Stokes
The investigators used the 21% relative risk reductions for both stroke and major bleeding with the use of apixaban (Eliquis), compared with warfarin in the ARISTOTLE trial (N. Engl. J. Med. 2011;365:981-92), and applied those relative risk reductions to 23,525 managed care patients with atrial fibrillation on warfarin for stroke prevention in the Medco claims database. They found that the use of apixaban instead of warfarin would result in an estimated 1.1 fewer strokes and 2.1 fewer major bleeding events excluding intracranial hemorrhage per 100 person-years of follow-up in a real-world population, said Mr. Stokes of Evidera, a health care consulting firm in Montreal.
In contrast, applying the relative risk figures for dabigatran (Pradaxa) obtained from the RE-LY trial (N. Engl. J. Med. 2009;361:1139-51) yielded estimates of 1.9 fewer strokes but 0.7 additional major bleeding events per 100 person-years, compared with warfarin in everyday practice. For rivaroxaban (Xarelto), the data from the ROCKET-AF trial (N. Engl. J. Med. 2011;365:883-91) pointed to 0.8 fewer strokes than with warfarin, but 1.4 more major bleeding events, he continued.
For the key outcome of total medical costs saved through avoidance of stroke or major bleeding through the use of a NOAC rather than warfarin, the estimates were $1,245/year for a patient on apixaban and $555 for dabigatran. In contrast, rivaroxaban was not associated with a savings, but rather with an increase in medical costs of $144 per patient per year.
These are figures that take some of the sting out of the high prescription costs for the NOACs. The savings estimates relied upon incremental 1-year medical cost figures of $44,792/stroke and $35,829/major bleeding event, excluding intracranial hemorrhage, which were obtained from another study (Stroke 2011;42:112-8).
Since patients on warfarin for stroke prevention in the Medco database were older and thus higher risk than those in the NOAC pivotal trials were, the total medical cost savings for each NOAC were larger in the new analysis. In one earlier analysis that relied upon reference rates from the clinical trials, the total medical cost savings estimate for each NOAC, compared with warfarin, was $485 per patient per year for apixaban, $179 for dabigatran, and $89 for rivaroxaban (J. Med. Econ. 2012;15:776-85).
Mr. Stokes’s analysis was carried out by Evidera with research funding from Bristol-Myers Squibb and Pfizer, which jointly developed apixaban.