Prescribing patterns and clinician preferences for direct oral anticoagulant use in unusual site venous thromboembolism: a cross-sectional analysis from the Direct oral anticoagulants in Unusual Site venous Thromboembolism (DUST) study

Background: Unusual site venous thromboembolism (USVTE) presents therapeutic challenges. Direct oral anticoagulants (DOACs) are increasingly prescribed despite limited evidence from clinical trials. Objectives: This cross-sectional analysis aimed to describe DOAC prescription patterns and rationale for choosing DOACs for USVTE treatment in real-life clinical practice. Methods: The Direct oral anticoagulants in Unusual Site venous Thromboembolism study (NCT03778502) is an international, multicenter, prospective, observational registry. Adult patients with objectively diagnosed USVTE (years 2018-2023) treated with DOACs were included. Information was collected on patient characteristics, USVTE location, anticoagulant treatment, and rationale for starting DOACs. Results: In total, 349 patients were included from 23 centers in 9 countries. The most common USVTE were splanchnic vein thrombosis (n = 219, 62.8%) and cerebral vein thrombosis (n = 103, 29.5%). The most prescribed DOACs were apixaban (n = 186, 53.3%) and rivaroxaban (n = 101, 28.9%). The median delay between USVTE diagnosis and DOAC initiation was 24 days, with 219 patients (62.8%) starting DOACs >14 days after diagnosis. Indeed, 320 (91.7%) patients received other anticoagulants before switching to DOACs (mainly low-molecular-weight heparin, n = 217, 67.8%). The main reasons for prescribing DOACs were oral administration (145/336, 43.2%), no need for blood monitoring (131/336, 39.0%), favorable safety profile (116/336, 34.5%), and prescriber-reported patient's preference (96/336, 28.6%). Apixaban was the most prescribed DOAC in splanchnic vein thrombosis (133/219, 60.7%), while dabigatran was the most prescribed DOAC in cerebral vein thrombosis (38/103, 36.9%). Conclusion: DOACs are increasingly prescribed for USVTE owing to their ease of use and perceived safety, but mainly after initial treatment with parenteral anticoagulation. Further evidence is still needed to support their use in the acute phase.