The best treatment of an acute episode of VTE is its prevention (thromboprophylaxis). Although previous clinical trials have shown some benefit on the use of thromboprophylaxis in ambulatory cancer patients, these studies have been inconclusive to convincingly demonstrate that existing anticoagulants significantly reduce the rate of VTE in cancer patients. Possible explanations are related to the fact that these studies have included a large number of cancer patients whose risk for VTE has been low and in consequence, the benefit of anticoagulation has become diluted by the large proportion of low risk cancer patients.