Primary prevention of cancer-associated venous thrombosis: Rationale and challenges in clinical practice

•Cancer-associated thrombosis (CAT) jeopardizes a patient's prognosis.•The available scores of CAT risk are poorly reproductible over cancer types.•The decision of thromboprophylaxis should be made on a case-by-case basis.•Low molecular weight heparin is recommended in most eligible patients.•Alternate choices should consider the risks of bleeding, frailty and/or DDI.