Extremely high levels of von Willebrand factor antigen and of procoagulant factor VIII found in multiple myeloma patients are associated with activity status but not with thalidomide treatment.

Venous thromboembolism (VTE) is a major complication in patients with multiple myeloma (MM) during treatment with thalidomide combined with chemotherapy and/or dexamethasone. The pathophysiology is not clear. We performed a cross-sectional study in 20 MM patients who were treated with thalidomide for refractory/relapsed disease. Seven patients (35%) experienced an episode of VTE. Plasma samples were analyzed for known risk factors for VTE and compared with those from 30 MM patients without thalidomide treatment. The patients groups differed in their baseline characteristics in activity status only. Extremely high levels of factor VIII-coagulant activity (FVIII:C, mean 352%) and von Willebrand factor antigen (VWF-Ag, 374%) were found in all patients using thalidomide. All other prothrombotic risk factors were normal. In patients with VTE, VWF-Ag but not FVIII:C, levels were significantly higher as compared with patients without VTE. Patients without thalidomide treatment had significantly lower levels of both coagulation factors but the difference was only due to difference in activity status. High FVIII:C/VWF-Ag levels are found in patients with active MM and this is probably a reflection of increased bone marrow angiogenesis in MM. These prothrombogenic circumstances could contribute to the high incidence of VTE during treatment with thalidomide in combination with dexamethasone/chemotherapy.