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Cancer is a leading cause of venous thromboembolism (VTE) and vice versa. Pulmonary embolism is the second cause of death in cancer patients. Tumor progression is associated with coagulation activation. The pathogenesis of thrombosis during cancer is particularly complex stemming from multiple connections of this disease with both systems of inflammation and hemostasis. The risk of VTE depends on cancer type and the stage of the disease, the anticancer treatments and the time since cancer diagnosis as well as on the presence of patient-related risk factors (i.e. age, obesity, previous history of VTE, underlying diseases…). The presence of other precipitating factors and the duration of the exposure to them are also key elements in the assessment of such a thrombotic risk. It is therefore important to identify all the VTE risk factors to identify patients at high vascular risk and to determine the period during which this risk is significantly increased. The integration of biomarkers of hypercoagulability in proposed risk assessment models for VTE will improve their capacity to identify patients eligible for pharmacological thromboprophylaxis. In this review, we report the current status of knowledge on the connection between cancer and hypercoagulability, the numerous risk factors for VTE must be identified in cancer patients and the best methodology to build a more accurate assessment of this vascular risk in such a complex medical context.

Large epidemiological studies have shown that nearly all risk factors for deep vein thromboses have a different impact on the manifestation of the disease, which aids in their differentiation into high, moderate and low risk. North American authors have introduced a fourth class of very high risk. The prophylactic measures available are numerous. They can be used in isolation or association depending on the significance of the risk. In France, prophylaxis by LMWH (low molecular weight heparin) is by far the most frequently used method. Recently, apart from compression stockings and intermittent mechanical compression, the use of footpumps, and a technique of electrical calf stimulation have been proposed. Each thrombosis center or service should put in place a well defined strategy for prescribing thromboprophylaxis, adapted to the level of the thromboembolic risk for each group of patients. A dose of LMWH higher than that used for a moderate risk is indicated for most LMWH, in the case of a high or very high risk. A few problems still exist: the pre or postoperative timing of the first injection, the duration of the prophylaxis particularly during the post-discharge period, and the evaluation of the risk in certain situations such as laparoscopic surgery or limb immobilization, for which the studies are too few to formulate recommendations from the level of evidence available. The socioeconomic realities of using LMWH should not be ignored.