Apart from myeloma, primary prophylaxis of venous thromboembolism (VTE) in ambulatory cancer patients treated with chemotherapy is underused, despite its proven benefit for pancreatic cancer and to a lesser extent for lung cancer. This prophylaxis has been showed to be effective for myeloma, pancreas but in absolute numbers these cancers lead to a few venous thromboembolic events. Up to date, VTE risk scores cannot be used as a discriminatory criterion to select a high-risk population that could really benefit from this prevention. VTE depends in part on oncogenic mutations of tumor cells that result in an imbalance between activation and inhibition pathways that are involved in venous thrombus formation. So, stratification of risk of VTE in cancer patients could be considered from a clinical and molecular point of view and result in a tailored prophylaxis. This "personalized medicine" that is currently used for the anti-tumor treatment of many cancers and hematological malignancies, could lead to a more effective prophylaxis of VTE in cancer patients.