This trial was performed within the frame of the Austrian Study on Recurrent Venous Thromboembolism (AUREC), an ongoing prospective cohort study . Between July 1992 and September 2008, consecutive patients with a first distal and/or proximal deep-vein thrombosis of the leg and/or pulmonary embolism who had been treated with anticoagulants for 3 to 18 months were included. Three weeks after withdrawal of anticoagulation, women were screened for biochemical and genetic risk factors of venous thromboembolism (VTE). The present prospective analysis included data collected until March 2012. The cohort was composed of 630 women (333 estrogen users, 297 non-users, average age 46 ± 17 years) with a first VTE who were followed for an average of 69 months after anticoagulation withdrawal. Excluded were women with a previous or secondary VTE; coagulation inhibitor deficiency; lupus anticoagulant; cancer; pregnancy; requirement of long-term antithrombotic therapy; or homozygosity or double heterozygosity for factor V Leiden and/or the G20210A prothrombin mutation. The endpoint was objectively documented symptomatic recurrent VTE. VTE recurred in 22 (7%) estrogen users and in 49 (17%) non-users. After 1, 2 and 5 years, the cumulative probability of recurrence was 1% (95% confidence interval (CI) 0–2), 1% (95% CI 0–2) and 6% (95% CI 3–9) among estrogen users and 5% (95% CI 2–7), 9% (95% CI 6–13) and 17% (95% CI 12–22) among non-users. Compared to non-users, estrogen users had an adjusted relative risk (RR) of recurrent VTE of 0.4 (95% CI 0.2–0.8). Compared to non-users in the respective age groups, the RR of recurrence was 0.4 (95% CI 0.2–0.8) among estrogen-containing contraceptive users and 0.7 (95% CI 0.3–1.5) among women using estrogen-containing menopausal hormone therapy. The study conclusions were therefore that women who had their first VTE while using estrogens have a low risk of recurrent VTE. These women might not benefit from extended anticoagulant therapy.
Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
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