Pathophysiology of the thrombophilic state in the cancer patient.

The "hypercoagulable state" of malignancy is due to a complex interaction of tumor cells and their products with host cells, leading to various degrees of impairment of the normal defense mechanisms that ordinarily protect the host against thrombogenesis. Tumor cells can activate directly the blood clotting cascade and cause thrombosis or can induce procoagulant properties and inhibit anticoagulant properties of vascular endothelial cells, platelets, and monocytes and macrophages. In the setting of the local and systemic effects of cancer (e.g., stasis induced by prolonged bed rest and/or vascular invasion by tumor), together with iatrogenic complications of the treatment of cancer (e.g., the use of central vein catheters and angiopathic chemotherapy), this basic pathophysiology conspires to make cancer perhaps the best example of "acquired thrombophilia." In this brief review, we have attempted to describe what is currently known about the mechanisms for the hypercoagulable state of cancer and provide a summary of the evidence that indicates the many levels of defects in patients with malignancies that predispose them to thrombosis. A better understanding of the pathophysiology of thrombophilia in cancer should provide clinicians with an improved rationale for more aggressive and specific anticoagulant strategies in selected patients.