ASH 2010: A New Scoring System Assesses the Risk of Recurrent Venous Thromboembolism

A new scoring system has been developed that is designed to predict the risk of recurrent venous thromboembolism (VTE) in a patient with cancer. The new system will be validated in a prospective multicenter study, which will also evaluate different treatment strategies according to patients’ perceived risk, explained lead author Martha L. Louzada, MD, University of Western Ontario, Department of Medicine, London Health Sciences Center, London, Ontario, Canada.

“The development of a scoring system that stratifies VTE recurrence risk in patients with cancer-associated VTE is important as the first step in demonstrating that such a heterogeneous population varies in terms of VTE recurrence risk,” Louzada stated. “With better treatment methods, the standard of care for cancer patients can be improved as physicians will be able to better predict the risk of VTE recurrence in patients with cancer-associated VTE and plan treatment accordingly.”

VTE is a major, life-threatening complication of cancer and some cancer therapies; it encompasses deep vein thrombosis and pulmonary embolism. Patients with cancer have a 1 in 250 incidence of experiencing a VTE event compared with an incidence of 1 in 1000 for patients without cancer. Louzada said patients with cancer are at higher risk for VTE because of disease-related factors that lead to overactivity of the blood clotting system. The rate of VTE recurrence ranges from 7% to 13% for patients with cancer compared with 2% in patients without cancer.

Current guidelines recommend that all patients with cancer who have experienced a VTE previously receive low-molecular weight heparin (LMWH) for at least 6 months, and experts believe anticoagulants should be continued while treatment is ongoing or as long as the patient has cancer. Currently, definitive data are lacking to determine whether strategies for VTE prophylaxis should vary according to a cancer patient’s risk of VTE or whether patients at low risk of recurrent VTE would benefit from oral anticoagulation using a vitamin K antagonist, which is often used to treat noncancerous patients who have experienced VTE.

The retrospective study was based on a review of charts for 543 patients with cancer who suffered a VTE and were followed from 2001 to 2004 and from 2007 to 2008 at the Ottawa Hospital in Ontario, Canada. During the first 6 months of therapy with an anticoagulant, 10.1% of patients developed VTE. Of the patients treated with standard LMWH, 10.1% (36 of 343) experienced recurrent VTE compared with 9.5% (19 of 200) of patients treated with a vitamin K antagonist. Louzada said this suggests that the type of anticoagulation therapy did not have a significant effect on recurrent VTE.

In a multivariate analysis, gender, primary tumor site, tumor stage, and history of prior VTE were identified as significant factors in predicting recurrent VTE. Female gender, lung cancer, and prior history of VTE increased the risk of recurrence while breast cancer and stage I disease appeared to be associated with lower risk of recurrence (Table).

A risk factor scoring system for recurrent VTE was developed from this model, with scores ranging from -3 to 3. Low risk for recurrent VTE was defined as a score of -3 to 0, indicating a 4.5% risk; 48% of patients were assessed as low risk. Patients with a score of 1 to 3 were considered high risk and had a risk of VTE recurrence >19.7%.