Aspirin Plus a DOAC May Do More Harm Than Good in Some

Sharon Worcester

December 09, 2019

ORLANDO, Florida — Combining aspirin and direct oral anticoagulant (DOAC) therapy for the secondary prevention of venous thromboembolism (VTE) or the prevention of stroke associated with nonvalvular atrial fibrillation (NVAF) without a clear indication was associated with increased bleeding risks in a large registry-based cohort.

The study, which involved a cohort of 2045 patients who were followed at six anticoagulation clinics in Michigan during January 2009 to June 2019, also found no apparent improvement in thrombosis incidence with the addition of aspirin, Jordan K. Schaefer, MD, reported during a press briefing at the annual meeting of the American Society of Hematology.

Of the cohort patients, 639 adults who received a DOAC plus aspirin after VTE or for NVAF without a clear indication were compared with 639 propensity-matched controls. The bleeding event rate per 100 patient years was 39.50 vs 32.32 at an average of 15.2 months of follow-up in the combination therapy and DOAC monotherapy groups, respectively, said Dr Schaefer of the division of hematology/oncology, department of internal medicine, University of Michigan, Ann Arbor.

"This result was statistically significant for clinically relevant non-major bleeding, with an 18.7 rate per 100 patient years, compared with 13.5 for DOAC monotherapy," (P = .02), he said. "We also saw a significant increase in non-major bleeding with combination therapy, compared with direct oral anticoagulant monotherapy" (rate, 32.82 vs 25.88; P = .04).

No significant difference was seen overall (P = .07) or for other specific types of bleeding, he noted.

The observed rates of thrombosis in the groups, respectively, were 2.35 and 2.23 per 100 patient years (P = .95), he said, noting that patients on combination therapy also had more emergency department visits and hospitalizations, but those differences were not statistically significant.

"Direct-acting oral anticoagulants, which include apixaban, dabigatran, edoxaban, and rivaroxaban, are increasingly used in clinical practice for indications that include the prevention of strokes for patients with nonvalvular atrial fibrillation, and the treatment and secondary prevention of venous thromboembolic disease," Dr Schaefer said.

Aspirin is commonly used in clinical practice for various indications, including primary prevention of heart attacks, strokes, and colorectal cancer, as well as for thromboprophylaxis in patients with certain blood disorders or with certain cardiac devices, he added.

"Aspirin is used for the secondary prevention of thrombosis for patients with known coronary artery disease, peripheral artery disease, or carotid artery disease," he said. "And while adding aspirin to a DOAC is often appropriate after acute coronary syndromes or percutaneous coronary intervention, many patients receive the combination therapy without a clear indication, he said, noting that increasing evidence in recent years, largely from patients treated with warfarin and aspirin, suggest that the approach may do more harm than good for certain patients.

Specifically, there's a question of whether aspirin is increasing the rates of bleeding without protecting patients from adverse thrombotic outcomes.

"This has specifically been a concern for patients who are on full-dose anticoagulation," he said.

In the current study, patient demographics, comorbidities, and concurrent medications were well balanced in the treatment and control groups after propensity score matching, he said, noting that patients with a history of heart valve replacement, recent MI, or less than 3 months of follow-up were excluded.

"These findings need to be confirmed in larger studies, but until such data [are] available, clinicians and patients should continue to balance the relative risks and benefits of adding aspirin to their direct oral anticoagulant therapy," Dr Schaefer said. "Further research needs to evaluate key subgroups to see if any particular population may benefit from combination therapy compared to DOAC therapy alone."

Schaefer has disclosed no relevant financial relationships.

American Society of Hematology (ASH) 2019: Abstract 787. Presented December 9, 2019.

This article first appeared on MDEdge.com.

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