Comparison of 3 and 6 months of oral anticoagulant therapy after a first episode of proximal deep vein thrombosis or pulmonary embolism and comparison of 6 and 12 weeks of therapy after isolated calf deep vein thrombosis

Background-The optimal duration of oral anticoagulant therapy after a first episode of venous thromboembolism remains controversial. Methods and Results-We performed an open-label, randomized trial comparing a short oral anticoagulant course (3 months for proximal deep vein thrombos is [P-DVT] and/or pulmonary embolism [PE], 6 weeks for isolated calf DVT [C -DVT]) with a long course of therapy (6 months for P-DVT/PE; 12 weeks for C -DVT), The outcome events were recurrences and major, minor, or fatal bleed ing complications. A total of 736 patients were enrolled. There were 23 rec urrences of venous thromboembolism in the short treatment group (6.4%) and 26 in the long treatment group (7.4%); the 2 treatment regimens had an equi valent effect. For the hemorrhage end point, the difference between the sho rt and the long treatment groups was not significant: 15.5% versus 18.4% fo r all events (P=0.302), 1.7% versus 2.8% (P=0.291) for major events, and 13 .9% versus 15.3% for minor bleeding. Subgroup analysis demonstrated that th e rate of recurrence was lower for C-DVT than for P-DVT or PE, Conclusions-After isolated C-DVT, 6 weeks of oral anticoagulation is suffic ient. For P-DVT or PE, we demonstrated an equivalence between 3 and 6 month s of anticoagulant therapy. For patients with temporary risk factors who ha ve a low risk of recurrence, 3 months of treatment seems to be sufficient. For patients with idiopathic venous thromboembolism or permanent risk facto rs who have a high risk of recurrence, other trials are necessary to assess prolonged therapy beyond 6 months.