Risk assessment for cancer-associated thrombosis: what is the best approach?

Venous thromboembolism (VTE) is an increasingly frequent complication of cancer and its treatments. One in five cancer patients are estimated to develop venous and arterial events during the natural history of their illness. However, the risk for VTE varies widely between various subgroups of cancer patients and even in the same cancer patient over time. This narrative review focuses on risk factors, biomarkers and risk assessment tools and attempts to clarify approaches to risk stratification. Clinical risk factors include primary site of cancer, chemotherapy, anti-angiogenic therapy, surgery and hospitalization. Predictive and candidate biomarkers include platelet and leukocyte counts, hemoglobin, D-dimer and tissue factor. However, single risk factors or biomarkers have not, in general, been able to identify sufficiently high-risk populations. A clinical risk score, incorporating 5 simple clinical and laboratory variables, has now been studied in over 10,000 patients and can successfully categorize patients at low- and high-risk for VTE. Recent trials have shown that outpatient prophylactic anticoagulation is both safe and effective, but event rates have been highly variable. Targeted thromboprophylaxis provides an optimal risk-benefit ratio and the best opportunity to reduce the burden of VTE and its consequences for patients with cancer.