GI Bleeding and Colorectal Cancer Risk in Anticoagulated AF Patients

Study Questions:

What is the risk of occult colorectal cancer in patients with atrial fibrillation (AF) treated with oral anticoagulation therapy (OAC) who experience gastrointestinal (GI) bleeding?


The authors explored 125,418 Danish patients with AF from nationwide administrative records. All patients received OAC therapy after an AF diagnosis. The primary exposure was lower GI bleeding and the primary outcome was a diagnosis of colorectal cancer according to International Classification of Diseases, 10th Revision (ICD-10) codes. Regression analysis was adjusted for age and time since OAC initiation.


During a maximum of 3 years of follow-up, 2,576 patients experienced lower GI bleeding, of whom 140 were subsequently diagnosed with colorectal cancer. Absolute 1-year risk of colorectal cancer following GI bleeding in this population ranged from 3.7% (95% confidence interval [CI], 2.2-6.2%) in patients ≤65 years old to 8.1% (95% CI, 6.1-10.6%) in patients 76-80 years old. The risk ratio of subsequent colorectal cancer diagnosis among patients with GI bleeding vs. those without GI bleeding ranged from 24.2 (95% CI, 14.5-40.4) for patients <65 years old to 12.3 (95% CI, 7.9-19.0) for patients >85 years old.


The authors concluded that a lower GI bleed among anticoagulated patients with AF confers a high risk of incident colorectal cancer.


Although OAC therapy does not cause bleeding on its own, it does increase the likelihood of bleeding when an underlying pathology is present. That may be the main message from this Danish nationwide analysis of patients with AF who experience lower GI bleeding. Rather than dismiss any change in stools following OAC initiation, clinicians should carefully consider the role of colorectal cancer screening when lower GI bleeding occurs without another clear etiology (e.g., known hemorrhoids).

Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Cardio-Oncology, Geriatric Cardiology, Prevention, Anticoagulation Management and Atrial Fibrillation, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Anticoagulants, Arrhythmias, Cardiac, Atrial Fibrillation, Cardiotoxicity, Colorectal Neoplasms, Early Detection of Cancer, Gastrointestinal Hemorrhage, Geriatrics, Hemorrhoids, Risk, Secondary Prevention

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