Apixaban Outmatches Rivaroxaban
for VTE in Study

Will Pass

December 07, 2021

Apixaban appears to be safer and more effective than rivaroxaban for reducing risk of venous thromboembolism and bleeding, based on new research.

Recurrent venous thromboembolism (VTE) — a composite of pulmonary embolism and deep vein thrombosis — was the primary effectiveness outcome in the retrospective analysis of new-user data from almost 40,000 patients, which was published in Annals of Internal Medicine. Safety was evaluated through a composite of intracranial and gastrointestinal bleeding.

After a median follow-up of 102 days in the apixaban group and 105 days in the rivaroxaban group, apixaban demonstrated superiority for both primary outcomes.

These real-world findings may guide selection of initial anticoagulant therapy, reported lead author Ghadeer K. Dawwas, PhD, MSc, MBA, of the University of Pennsylvania, Philadelphia, and colleagues.

"Randomized clinical trials comparing apixaban with rivaroxaban in patients with VTE are under way (for example, COBRRA (NCT03266783)," the investigators wrote. "Until the results from these trials become available (The estimated completion date for COBRRA is December 2023.), observational studies that use existing data can provide evidence on the effectiveness and safety of these alternatives to inform clinical practice."

In the new research, apixaban was associated with a 23% lower rate of recurrent VTE (hazard ratio, 0.77; 95% confidence interval, 0.69-0.87), including a 15% lower rate of deep vein thrombosis and a 41% lower rate of pulmonary embolism. Apixaban was associated with 40% fewer bleeding events (HR, 0.60; 95% CI, 0.53-0.69]), including a 40% lower rate of GI bleeding and a 46% lower rate of intracranial bleeding.

The study involved 37,236 patients with VTE, all of whom were diagnosed in at least one inpatient encounter and initiated direct oral anticoagulant (DOAC) therapy within 30 days, according to Optum's deidentified Clinformatics Data Mart Database. Patients were evenly split into apixaban and rivaroxaban groups, with 18,618 individuals in each. Propensity score matching was used to minimize differences in baseline characteristics.

Apixaban was associated with an absolute reduction in recurrent VTE of 0.6% and 1.1% over 2 and 6 months, respectively, as well as reductions in bleeding of 1.1% and 1.5% over the same respective time periods.

The investigators noted that these findings were maintained in various sensitivity and subgroup analyses, including a model in which patients with VTE who had transient risk factors were compared with VTE patients exhibiting chronic risk factors.

"These findings suggest that apixaban has superior effectiveness and safety, compared with rivaroxaban and may provide guidance to clinicians and patients regarding selection of an anticoagulant for treatment of VTE," Dawwas and colleagues concluded.

Study May Have Missed Some Nuance in Possible Outcomes, According to Vascular Surgeon

Thomas Wakefield, MD, a vascular surgeon and a professor of surgery at the University of Michigan Health Frankel Cardiovascular Center, Ann Arbor, generally agreed with the investigators' conclusion, although he noted that DOAC selection may also be influenced by other considerations.

"The results of this study suggest that, when choosing an agent for an individual patient, apixaban does appear to have an advantage over rivaroxaban related to recurrent VTE and bleeding," Wakefield said in an interview. "One must keep in mind that these are not the only factors that are considered when choosing an agent and these are not the only two DOACs available. For example, rivaroxaban is given once per day while apixaban is given twice per day, and rivaroxaban has been shown to be successful in the treatment of other thrombotic disorders."

Wakefield also pointed out that the study may have missed some nuance in possible outcomes.

"The current study looked at severe outcomes that resulted in inpatient hospitalization, so the generalization to strictly outpatient treatment and less severe outcomes cannot be inferred," he said.

Damon E. Houghton, MD, of the department of medicine and a consultant in the department of vascular medicine and hematology at Mayo Clinic, Rochester, Minn., called the study a "very nice analysis," highlighting the large sample size.

"The results are not a reason to abandon rivaroxaban altogether, but do suggest that, when otherwise appropriate for a patient, apixaban should be the first choice," Houghton said in a written comment. "Hopefully this analysis will encourage more payers to create financial incentives that facilitate the use of apixaban in more patients."

Randomized Trial Needed, Says Hematologist

Colleen Edwards, MD, of the departments of medicine, hematology, and medical oncology, at the Icahn School of Medicine at Mount Sinai, New York, had a more guarded view of the findings than Wakefield and Houghton.

"[The investigators] certainly seem to be doing a lot of statistical gymnastics in this paper," Edwards said in an interview. "They used all kinds of surrogates in place of real data that you would get from a randomized trial."

For example, Edwards noted the use of prescription refills as a surrogate for medication adherence, and emphasized that inpatient observational data may not reflect outpatient therapy.

"Inpatients are constantly missing their medicines all the time," she said. "They're holding it for procedures, they're NPO, they're off the floor, so they missed their medicine. So it's just a very different patient population than the outpatient population, which is where venous thromboembolism is treated now, by and large."

Although Edwards suggested that the findings might guide treatment selection "a little bit," she noted that insurance constraints and costs play a greater role, and ultimately concluded that a randomized trial is needed to materially alter clinical decision-making.

"I think we really have to wait for randomized trial before we abandon our other choices," she said.

The investigators disclosed relationships with Merck, Celgene, UCB, and others. Wakefield reported awaiting disclosures. Houghton and Edwards reported no relevant conflicts of interest.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.


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