Extended anticoagulation for unprovoked venous thromboembolism: a majority of patients should be treated.

About half of patients with a first unprovoked proximal deep vein thrombosis (DVT) or pulmonary embolism (PE) will have a recurrent venous thromboembolism (VTE) within 10 years if they stop treatment, and randomized trials have shown clear benefit from extended anticoagulant therapy in these patients. Although the risk of recurrence varies among patients with a first unprovoked proximal DVT or PE, and a number of factors can identify patients with a lower risk of recurrence, the safety of routinely stopping anticoagulant therapy based on the presence of these factors needs to be established in prospective studies before this is done in clinical practice. As isolated distal DVT is associated with about half the risk of recurrence of proximal DVT or PE, a first episode of unprovoked distal DVT does not justify extended anticoagulation. High risk for bleeding, and patient preference, are good reasons not to treat unprovoked proximal DVT or PE indefinitely. New anticoagulants, because they are easier to use and may be associated with less bleeding that vitamin K antagonists, have the potential to increase the proportion of patients with unprovoked VTE who are candidates for extended anticoagulant therapy.