Biological and clinical aspects of anticancer effects of antithrombotics.

Hemostatic mechanisms play a role not only in cancer associated thrombotic diathesis, but also in tumor growth and dissemination. Hence, inhibition of fibrin formation has been considered a possible tool against the progression of malignant disease. An antineoplastic effect of antithrombotic agents in various experimental models (i.e. tumor cell in culture, experimental animals, and cancer patients) has often been suggested. Anticoagulant drugs such as heparins and vitamin K antagonists have been repeatedly tested in this context. However, heparins have been more extensively studied. Several reports in animal models demonstrate that heparin can reduce the primary tumor growth or its metastatic spread. Clinical studies of thrombosis in cancer patients show that, besides their role as antithrombotics, heparins may have beneficial effects on survival in these patients, with a major role for low molecular-weight heparin (LMWHs) compared to unfractionated heparin (UFH). More recently a number of prospective randomized clinical trials of LMWH for survival as a primary end-point in cancer patients have been conducted, showing favourable results.