The association between
thrombosis and
cancer has been extensively studied since first pointed out by Trousseau in 1895. It is, however, not commonly appreciated that the incidence of
thrombosis in malignant hematologic disorders is as high or even higher than in solid
tumors. Thrombotic complications in acute
leukemia are often overlooked because
bleeding complications generally dominate the clinical picture. Yet, the patient is at risk for both. While there are many thrombogenic factors shared by both solid
tumors and
leukemia, many additional prothrombotic features are present in
leukemia. The prothrombotic factors include hyperleukocytosis, increased expression of
tissue factor and its activation in leukemic cells, and the prothrombotic adverse effects of therapeutic agents and vascular access
catheters. In addition, comorbid conditions including
hereditary thrombophilia,
infection, endothelial cell activation by
cytokines,
antiphospholipid syndrome and acquired
activated protein C resistance are major contributory factors. Factors that increase the
bleeding risk include
thrombocytopenia,
disseminated intravascular coagulation, and excessive fibrinolysis, which is enhanced by increased expression of
Annexin II by leukemic cells. Therapeutic approaches to both
bleeding and thrombotic conditions require special considerations of these factors.