Bleeding events in Asian patients with cancer-associated thrombosis: a 10-year single-centre experience

Malignancy is a well-recognised major risk factor for venous thromboembolism (VTE). While anticoagulation is the cornerstone of management for cancer-associated thrombosis (CAT), its use is associated with an increased risk of bleeding. This study aimed to determine the incidence of bleeding, patterns of anticoagulant use, and bleeding outcomes, and to identify factors associated with bleeding events during the first 6 months of CAT treatment. We conducted a retrospective study on cancer patients in Hospital Canselor Tuanku Muhriz (HCTM) who were diagnosed with pulmonary embolism (PE) and/or deep vein thrombosis (DVT) and received anticoagulant therapy from January 2015 to January 2025. Medical records and clinical laboratory data were collected and analysed. The primary outcome was the incidence of bleeding events, including major bleeding and clinically relevant non-major bleeding, as defined by the ISTH. A total of 203 patients were included. The most common anticoagulant used during the study period was DOACs (66%), followed by parenteral anticoagulants (low molecular weight heparin LMWH and fondaparinux) (28.1%) and warfarin (5.9%). The incidence of bleeding within six months of anticoagulation was 25.1% (51/203). The incidence of bleeding events was 24% among patients with non-haematological malignancies, compared with 33.3% among those with haematological malignancies. Bleeding was most frequently observed among patients receiving vitamin K antagonist, warfarin (41.6%), followed by parenteral anticoagulants (LMWH and fondaparinux) (33.3%), while the lowest proportion occurred among DOAC users (20.2%). The gastrointestinal tract was the most common site of bleeding (45%). During treatment, 6% of patients initially on DOACs were converted to LMWH, predominantly due to bleeding events or increased bleeding risk. Nearly half of bleeding episodes occurred within the first month of treatment (median 31.5 days). Prolonged INR during bleeding event (INR > 1.5) was the only significant associated risk factor for bleeding (OR 2.42, p = 0.016). Overall, these findings highlight the need for individualised anticoagulation strategies in cancer-associated thrombosis, particularly in Asian populations.