Anticoagulant-related bleeding as a sign of underlying tumoural lesions in patients with atrial fibrillation: a nationwide cohort study.

Aims: Bleeding events are a well-known complication of oral anticoagulant (OAC) use in patients with atrial fibrillation (AF). While these are undesirable, bleedings could have a warning potential for underlying tumoural lesions. Therefore, we aimed to investigate the association between anticoagulant-related bleeding and newly diagnosed tumoural lesions in a nationwide cohort study.

Methods and results: Using Belgian nationwide data, AF patients without any tumoural lesions were included when initiating OACs between 2013 and 2019. The absolute and relative risks of newly diagnosed tumoural lesions were investigated in OAC users with vs. without an OAC-related bleeding event. Analyses were additionally stratified by tumoural lesion, location-specific bleeding, and OAC type. A total of 230 386 OAC users were included, among whom 35 192 persons were diagnosed with a tumoural lesion during follow-up. Persons with a clinically relevant bleeding during OAC use had a tumoural lesion incidence of 15.33 per 100 person-years compared to an incidence of 5.22 per 100 person-years in persons without bleeding. Site-specific gastrointestinal, urogenital, respiratory, and intracranial bleeding events were respectively associated with a significantly increased risk of incident gastrointestinal [adjusted hazard ratio (aHR) 8.13 (95% confidence interval (CI): 7.08-9.34)], urological [aHR 12.73 (95% CI: 10.56-15.35)], respiratory [aHR 4.91 (95% CI: 3.24-7.44)], and intracranial tumoural lesions [aHR 27.89 (95% CI: 16.53-47.04)].

Conclusion: Bleeding events in AF patients initiated on OAC were associated with an increased risk of tumoural lesions. Therefore, OAC-related bleeding events could unmask an underlying tumoural lesion.