Patterns of Anticoagulation Use in Atrial Fibrillation and Active Cancer: Observations From Medicare

Introduction: Use of oral anticoagulation (OAC) in patients with atrial fibrillation (AF) and cancer is challenging due to increased thrombotic and bleeding risks, and data on prescription patterns are lacking. Hypothesis: Underutilization of OAC among patients with AF and cancer is associated with cancer specific factors. Methods: This study examined OAC use and factors associated with discontinuation of OAC among Medicare patients with AF and a new diagnosis of cancer from 2011-2016. We described OAC use patterns prior to and after a diagnosis of cancer. Logistic regression was used to evaluate clinical variables associated with discontinuation of OAC at time of cancer diagnosis and cox proportional hazards model was used to evaluate variables associated with discontinuation after diagnosis. Results: Among 44,769 patients with established AF and newly diagnosed cancer, 30.2% (n=13,508) were taking OAC at the time of cancer diagnosis. A total of 15,228 patients (34%) had an OAC prescription fill after index cancer diagnosis. Warfarin was the most commonly used OAC, but direct oral anticoagulant use increased over the study period. A total of 29.5% of patients had their OAC discontinued at the time of cancer diagnosis. Patients with gastric (OR 2.75, CI 2.12-3.57), pancreatic (OR 2.71, CI 2.15-3.41), and colorectal (OR 1.97, CI 1.70-2.28) cancer were most likely to have their OAC discontinued at diagnosis (Figure). Bleeding (HR1.37, CI 1.28-1.48) and chemotherapy (HR 1.38, CI 1.06-1.80) were associated with subsequent discontinuation in those who remained on OAC after diagnosis. Conclusions: Nearly 2 in 3 patients with established AF were not treated with OAC after cancer diagnosis despite an elevated stroke risk. Significant heterogeneity in OAC use exists depending on cancer type, baseline comorbidities, and chemotherapy use. Studies are needed to characterize the thrombotic and bleeding risks in this population to establish management guidelines.