Anticoagulants in thrombosis and cancer: the missing link

Many cancer patients reportedly have hypercoaguable state, with recurrent thrombosis due to the impact of cancer cells and chemotherapy on the coagulation cascade. A number of retrospective studies showed that cancer patients are at higher risk of developing venous thromboembolism. In addition to the pathological mechanisms associated with tumor-mediated increase in thrombotic events, cancer therapies including chemotherapy, immobilization, cancer surgery and the use of central venous catheters contribute toward a hypercoaguable state and are therefore independent risk factors of venous thromboembolism in cancer patients. Studies have demonstrated that unfractionated heparin or low molecular weight heparin (LMWH) interferes with various processes involved in tumor growth and metastasis. These processes might include fibrin formation, binding of heparin to angiogenic growth factors--such as basic fibroblast growth factor and VEGF--modulation of tissue factor, release of tissue factor pathway inhibitor and other mechanisms. Clinical trials have suggested an improved efficacy of LMWH, as compared with UFH on the survival of cancer patients with deep vein thrombosis. Similarly, the impact of warfarin on the survival of cancer patients with thromboembolic disorders was demonstrated. Recent studies from our laboratory defined the role of the LMWH (tinzaparin), warfarin, antifactor VIIa and recombinant tissue factor pathway inhibitor in the modulation of angiogenesis, tumor growth and tumor metastasis.