Risk of Ischemic Stroke and Major Bleeding in Patients with Atrial Fibrillation and Cancer

Background: Atrial fibrillation (AF) is an important risk factor for ischemic stroke. Cancer may increase the risk both of ischemic stroke and of bleeding. Less is known about risk of ischemic stroke and bleeding among cancer patients with AF, complicating the prevention of ischemic stroke in these patients. Methods: Register based cohort study comprising all Swedish patients hospitalized with a primary diagnosis of AF from July 1, 2005 until December 31, 2014. Patients with cancer diagnosis were compared to the rest of the cohort. We repeated the analysis focusing on recent cancer diagnosis and on cancer types prone to thromboembolism. Associations between predictor and outcome variables were analyzed with Cox regression. Results: The cohort consisted of 294,989 AF patients including 71,882 with prior cancer diagnosis. After adjustments, neither cancer diagnosis overall, recent cancer diagnosis, or any subgroup of cancer were associated with increased risk of ischemic stroke. Several cancer forms were however associated with risk of major bleedings, including risk of intracranial hemorrhage for patients with prostate cancer and risk of gastrointestinal bleeds for patients with colorectal and pancreatic cancer, adjusted hazard ratios with 95% confidence intervals 1.31 (1.06-1.62), 1.74 (1.53-1.97), and 2.86 (1.80-4.55) respectively. Conclusion: Cancer diagnosis was not associated with increased risk of ischemic stroke but several cancer forms were associated with risk of major bleedings in this large, Swedish cohort of AF patients. The results may have implications for prevention of ischemic stroke in these patients.