Anticoagulation-associated hemorrhage in atrial fibrillation as a marker of occult malignancy: a narrative review

Atrial fibrillation (AF) is the most common arrhythmia in adults and significantly increases the risk of stroke. Due to common threats like systemic inflammation and treatment-related cardiotoxicity, individuals with cancer have a noticeably increased chance of developing AF. Managing AF in this population presents dual challenges: reducing thromboembolic risk while minimizing bleeding complications. Traditionally, warfarin, a vitamin K antagonist, has been the most widely used anticoagulant. However, the emergence of direct oral anticoagulants (DOACs), which offer equal or superior efficacy compared to warfarin with fewer dietary and drug interactions, has shifted clinical practice. This narrative review explores the complex clinical relationship between AF, anticoagulation, and bleeding as a potential early indicator of occult cancer. An expanding body of evidence from extensive cohort studies and meta-analyses supports this association, showing a significantly increased risk of gastrointestinal, genitourinary, respiratory, and, to a lesser extent, intracranial bleeding in anticoagulated patients that may precede cancer diagnosis. Although bleeding is a recognized difficulty of oral anticoagulation, it may expose occult malignancy, resulting in timely detection of cancer and more favorable outcomes. Perhaps it is time to regard occult gastrointestinal bleeding for what it may be: an early warning sign of malignancy. The increased risk of both thromboembolism and bleeding in cancer patients poses a challenge in clinical practice. Though bleeding has increasingly been recognized as a potential harbinger of occult cancer, uniform guidelines for malignant lesion screening after a hemorrhagic episode remain to be established. It is essential to establish a solid, evidence-based therapeutic protocol to achieve the best possible treatment and results for patients.