Venous thromboembolism (VTE) with concurrent thrombocytopenia is frequently encountered in patients with cancer. Therapeutic anticoagulation in the setting of thrombocytopenia is associated with a high risk of hemorrhage. Retrospective analyses suggest the utility of modified-dose anticoagulation in this population. To assess the incidence of hemorrhage or thrombosis according to anticoagulation strategy, we performed a prospective, multicenter, observational study. Patients with active malignancy, acute VTE, and concurrent thrombocytopenia (platelet count <100 000/µL) were enrolled. The cumulative incidences of hemorrhage or recurrent VTE were determined considering death as a competing risk. Primary outcomes were centrally adjudicated and comparisons made according to initial treatment with full-dose or modified-dose anticoagulation. A total of 121 patients were enrolled at 6 hospitals. Seventy-five patients were initially treated with full-dose anticoagulation (62%) and 33 (27%) with modified-dose anticoagulation; 13 (11%) patients received no anticoagulation. Most patients who received modified-dose anticoagulation had a hematologic malignancy (31 of 33 [94%]) and an acute deep vein thrombosis (28 of 33 [85%]). In patients who initially received full-dose anticoagulation, the cumulative incidence of major hemorrhage at 60 days was 12.8% (95% confidence interval [CI], 4.9-20.8) and 6.6% (95% CI, 2.4-15.7) in those who received modified-dose anticoagulation (Fine-Gray hazard ratio, 2.18; 95% CI, 1.21-3.93). The cumulative incidence of recurrent VTE at 60 days in patients who initially received full-dose anticoagulation was 5.6% (95% CI, 0.2-11) and 0% in patients who received modified-dose anticoagulation. In conclusion, modified-dose anticoagulation appears to be a safe alternative to therapeutic anticoagulation in patients with cancer who develop deep vein thrombosis in the setting of thrombocytopenia.
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