Rivaroxaban May be Cost-Effective for A-fib Patients

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With rivaroxaban having been shown to be as effective as warfarin for preventing stroke in patients with atrial fibrillation (A-fib), the economic realities of substituting the more expensive oral factor Xa inhibitor will likely determine the extent of its use. An analysis published online May 31, 2012, ahead of print in the American Journal of Cardiology suggests that improvements in patients’ length and quality of life with rivoraxaban outweigh the extra cost, at least under certain assumptions.

Researchers led by Craig I. Coleman, PharmD, of the University of Connecticut School of Pharmacy (Storrs, CT), used data from the ROCKET-AF trial to estimate costs per quality-adjusted life years using a United States payer/Medicare perspective.

In ROCKET-AF, rivaroxaban was noninferior to warfarin in preventing stroke or systemic embolism in patients with high-risk A-fib, decreasing the risk of intracranial hemorrhage by 33%.

For their analysis, the authors estimated the cost of rivaroxaban at $205 per month vs. $39 per month for warfarin, including international normalized ratio (INR) monitoring (14 tests per year).

Modeling Cost-effectiveness

Using a Markov model, the base-case analysis consisted of A-fib patients 65 year of age who were at high risk for stroke and had no contraindications to anticoagulation. The lifetime treatment costs were almost $6,000 higher for rivaroxaban but the quality-adjusted life years were higher as well (table 1).

Table 1. Rivaroxaban vs. Warfarin

The investigators also took into account the incremental cost-effectiveness ratio (ICER), which is the ratio of the change in costs to the incremental benefits of a therapeutic intervention or treatment. The ICER for rivaroxaban was $27,498 per quality-adjusted life year. 

At the lowest range of rivaroxaban drug cost, $123, rivaroxaban became an economically dominant strategy. Conversely, when using the highest range of rivaroxaban cost, $300, the cost ratio was $70,823 per quality-adjusted life year, which exceeded a willingness-to-pay threshold of $50,000 per year.

Looking at the cost of rivaroxaban on a monthly basis, intracranial hemorrhage added to the cost effectiveness, resulting in a total cost of $50,846 per quality-adjusted life year when the monthly cost of intracranial hemorrhage care was at the low end of the plausible range ($2,000 per month). As the baseline risk of intracranial hemorrhage increased across the plausible range, the cost  -effectiveness ratio for rivaroxaban decreased to as low as $14,916 per quality-adjusted life year.

Similarly, ischemic stroke at a hazard ratio (HR) of greater than 1.04 resulted in rivaroxaban no longer being cost-effective, with an ICER as high as $133,511 per quality-adjusted life year at an HR of 1.17. Furthermore, assuming a willingness-to-pay threshold of $50,000 per quality-adjusted life year as being cost-effective, the ICER for rivaroxaban became less favorable as the HR for ischemic stroke and intracranial hemorrhage increased together.

Limitations, Assumptions Inherent in Model

The authors say their analytical model “has limitations that should be considered when interpreting the results.” For instance, the probability of ischemic stroke and major hemorrhage (including intracranial hemorrhage) and other adverse events was derived solely from the ROCKET-AF trial.

“Unfortunately, randomized controlled trial participants and data do not always accurately reflect real-life efficacy and safety because participants may exhibit superior medication adherence and receive more comprehensive follow-up,” Dr. Coleman and colleagues write.

Additionally, the authors note, it was assumed for the purpose of the model that any major bleeding would result in permanent discontinuation of rivaroxaban or warfarin and initiation of aspirin, which may not always be the case and would likely depend on individual patient factors.

The authors add that they did not include dabigatran or apixaban in the model “because of the desperate nature of the [A-fib] populations studied (lower CHADS2 scores) and methods used in their clinical trials compared to ROCKET-AF.” They conclude that “such a direct economic comparison at this time may be misleading to decision makers.”

Does Not Compute

But in a telephone interview with TCTMD, Michael D. Ezekowitz, MD, PhD, of Thomas Jefferson Medical College (Philadelphia, PA), said that while the economic analysis is interesting and timely given the approval late last year of rivaroxaban, the numbers essentially mean very little to clinicians or their A-fib patients.

“The problem in the United States, and this is true for other novel agents besides rivaroxaban, is that the cost to the patient depends on their insurance, which is highly variable,” Dr. Ezekowitz said. “But health -care systems in all likelihood will see fewer hospitalizations and fewer strokes and therefore in the long run derive financial benefit from these agents.”

Despite the authors’ assertion of the positive incremental cost-effectiveness ratio for rivaroxaban, Dr. Ezekowitz said it is very difficult to compute the financial implications of the introduction of new agents because there are so many different constituencies in clinical practice.

“That ratio is extremely complex, difficult to calculate, and frankly has very little relationship to clinical practice,” he said. “What we as clinicians are most concerned about is what patients have to pay. These studies are helpful in a sense, but they need to address the financial cost to the patient of these new agents, especially when we know that warfarin by comparison is pennies on the dollar. Studies of this kind are useful from a global perspective, but to the clinician they are really of no value whatsoever.”

Lee S, Anglade MW, Pham D, et al. Cost-effectiveness of rivaroxaban compared to warfarin for stroke prevention in atrial fibrillation. Am J Cardiol. 2012;Epub ahead of print.

Related Stories:

• New Oral Anticoagulants Top Warfarin in A-fib Stroke Prevention
• ROCKET AF Published: Rivaroxaban Matches Warfarin in Treating A-Fib Patients

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