Platelet transfusion and anticoagulation in haematological cancer-associated thrombosis and thrombocytopenia: the CAVEaT multi-centre prospective cohort.

BACKGROUND: Venous thromboembolism (VTE) in patients with thrombocytopenia represents a complex management challenge. OBJECTIVES: describe practice, document outcomes, and compare management to national guidelines. METHODS: We present a prospective multicentre cohort of 105 patients with haematological cancer, VTE within 28 days and platelets < 50x109 /L from 14 May 2019 to 24 April 2021 from 20 sites. RESULTS: median age was 64 and median initial platelet count 28 x 109 /L. Thromboses were: 46% catheter-associated, 11% lower limb, 33% pulmonary emboli (PE) and 10% other sites. Management was according to International Society for Thrombosis and Haemostasis (ISTH) guidance in 30 (47%) of 64 patients with high-risk thrombosis and 2 (5%) of low-risk thrombosis (catheter-associated or asymptomatic subsegmental PE). 12 patients (11%) received no anticoagulation. At 28 days Mortality was 15%, 8% experienced VTE progression, 7% experienced major bleeding, and 25% experienced clinically relevant non-major bleeding. 4 inferior vena cava filters were placed, 2 were later removed. The median number of platelet units transfused was 5 (range 0-53). 27% of patients had a change of management strategy by 28 days. There was no clear relationship between platelet transfusion threshold, anticoagulant dose reduction threshold and risk of thrombosis progression or major bleeding. CONCLUSIONS: This data set demonstrates the heterogeneity of approaches used in patients presenting with severe thrombocytopenia and acute thrombosis and confirms the high rates of bleeding in this cohort with thrombosis progression rates similar to the wider cancer-associated thrombosis population. Randomized data is required in order to inform the optimal management.