Venous thromboembolism (VTE) is a common complication in all types of cancer and adversely impacts cancer prognosis. Randomized controlled trials with primary thromboprophylaxis in cancer patients generally show effective VTE relative risk reductions of up to 60%. However, absolute risks of VTE were fairly low. Thromboprophylaxis should therefore only be recommended to cancer patients at highest risk of VTE, who may benefit most from prophylaxis. Predictive risk models to identify patients at a high risk of VTE are promising, however additional validation is required. An increasing proportion of cancer-associated VTE is formed by incidental VTE, with similar risk factors and clinical consequences. Randomized trials are not yet available, but it seems reasonable to treat incidental VTE similarly to symptomatic VTE. In a substantial proportion of patients with unprovoked VTE without known cancer at the time of VTE diagnosis, concomitant or occult cancer is identified. Studies have investigated the value of extensive screening over routine examinations alone for occult cancer. Although extensive screening may be able to identify more occult cancers, its clinical benefit over routine screening has not been demonstrated.
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