Low-Molecular-Weight Heparins in the Treatment of Cancer-Associated Thrombosis: A New Standard of Care?

Cancer patients are twice as likely to develop postoperative venous thromboembolism (VTE) than non-cancer patients undergoing the same surgical procedure. Causes of cancer-associated thrombosis include: the capacity of tumor cells and their products to interact with platelets, clotting, and fibrinolytic proteins. Aggressive antitumor therapy with agents such as platinum compounds, high-dose fluorouracil, mitomycin-C, tamoxifen, and growth factors increase the risk of cancer-associated thrombosis. Despite the high risk of VTE in patients with cancer, thromboprophylaxis in surgical and medical oncology patients is low. Initial therapy of VTE in patients with cancer is low-molecular-weight heparin (LMWH) or unfractionated heparin. Long-term secondary prophylaxis of VTE is generally accomplished with oral anticoagulants, primarily warfarin. Evidence supports the use of LMWH for prevention and treatment of cancer-associated thrombosis because it is more easily administered, does not require laboratory monitoring, has a lower risk of adverse events, and is more cost effective than unfractionated heparin. In addition, the antineoplastic effects of LMWH have been demonstrated, including direct antitumor, antiangiogenic, and immune system modulatory action. Each LMWH is a unique biological entity having product-specific molecular and structural attributes; therefore, different LMWHs cannot be given interchangeably. Continued investigation of LMWH therapy in patients with cancer is warranted.