Mona Al Banna, MB BCh, MSc
Atrial fibrillation is a known risk factor for stroke, increasing stroke risk 5-fold and mortality 2-fold compared to patients without atrial fibrillation. Cancer causing a hypercoagulable state is another well-known risk factor for stroke. Current guidelines recommend direct oral anticoagulants (DOACs) in patients with non-valvular atrial fibrillation. In patients with cancer who develop atrial fibrillation, warfarin or low-molecular weight heparin have traditionally been preferred over the direct oral anticoagulants.
In this study, Chan et al. investigated the effectiveness and safety of the DOACs when compared to warfarin in this population. A nationwide retrospective cohort study was performed using the Taiwan National Health Insurance Research Database. They identified 85,641 patients diagnosed with atrial fibrillation and treated with an anticoagulation over a 5-year period. Of those AF patients with a diagnosis of cancer, 6274 were treated with DOACs and 1681 were treated with warfarin. The DOAC group had a lower risk of ischemic stroke, acute myocardial infarction, major adverse limb events and venous thrombosis compared to the warfarin group. DOAC use was associated with a lower risk of ICH and major bleeding when compared to warfarin. Subgroup analysis was also performed to determine how different DOACs or different dosages of DOACs compared to warfarin. In general, there was lower risk of thrombotic events and major bleeding for DOACs over warfarin irrespective of DOAC type and whether it was standard-dose or low-dose. In addition, this benefit of DOACs over warfarin was consistent across patients with different types of cancer and at different stages of disease activity.
This study is relevant for several reasons. There is little known about this specific population group as they have typically been underrepresented in clinical trials. The use of anticoagulants in atrial fibrillation patients with cancer can be challenging given the potential increased risk of both thromboembolism and bleeding. Traditionally, low molecular weight heparin has been the preferred anticoagulant treatment modality for cancer patients given its potential antitumor and antimetastatic effects and favorable efficacy profile. However, its long-term subcutaneous administration can be inconvenient and can lead to non-adherence. This study adds further supportive evidence to using DOACs in this patient population. This is especially important when considering the practical difficulties of treating cancer patients on warfarin, including drug-drug interactions and an unstable INR due to renal or liver dysfunction or change in nutritional status with cancer progression.
It is important to note that this study was a retrospective review that was limited to an Asian population. Future prospective studies are needed enrolling cancer patients with atrial fibrillation to evaluate the efficacy and safety profile of DOACs versus warfarin.
