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Does the route of administration for estrogen hormone therapy impact the risk of venous thromboembolism? Estradiol transdermal system versus oral estrogen-only hormone therapy

Laliberté, François MA1; Dea, Katherine MA1; Duh, Mei Sheng MPH, ScD2; Kahler, Kristijan H. PhD, RPh3; Rolli, Melanie MD3; Lefebvre, Patrick MA1

doi: 10.1097/gme.0b013e3182175e5c
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Objective: The aim of this study was to quantify the magnitude of risk reduction for venous thromboembolism events associated with an estradiol transdermal system relative to oral estrogen-only hormone therapy agents.

Methods: A claims analysis was conducted using the Thomson Reuters MarketScan database from January 2002 to October 2009. Participants 35 years or older who were newly using an estradiol transdermal system or an oral estrogen-only hormone therapy with two or more dispensings were analyzed. Venous thromboembolism was defined as one or more diagnosis codes for deep vein thrombosis or pulmonary embolism. Cohorts of estradiol transdermal system and oral estrogen-only hormone therapy were matched 1:1 based on both exact factor and propensity score matching, and an incidence rate ratio was used to compare the rates of venous thromboembolism between the matched cohorts. Remaining baseline imbalances from matching were included as covariates in multivariate adjustments.

Results: Among the matched estradiol transdermal system and oral estrogen-only hormone therapy users (27,018 women in each group), the mean age of the cohorts was 48.9 years; in each cohort, 6,044 (22.4%) and 1,788 (6.6%) participants had a hysterectomy and an oophorectomy at baseline, respectively. A total of 115 estradiol transdermal system users developed venous thromboembolism, compared with 164 women in the estrogen-only hormone therapy cohort (unadjusted incidence rate ratio, 0.72; 95% CI, 0.57-0.91; P = 0.006). After adjustment for confounding factors, the incidence of venous thromboembolism remained significantly lower for estradiol transdermal system users than for estrogen-only hormone therapy users.

Conclusions: This large population-based study suggests that participants receiving an estradiol transdermal system have a significantly lower incidence of venous thromboembolism than do participants receiving oral estrogen-only hormone therapy.

This large population-based study suggests that women receiving transdermal estradiol have a significantly lower incidence of venous thromboembolism compared with women receiving oral estrogen-only hormone therapy.

Received December 21, 2010; revised and accepted February 3, 2011.

From the 1Groupe d'analyse Ltée, Montréal, Quebec, Canada; 2Analysis Group Inc, Boston, MA; and 3Novartis Pharmaceuticals Corporation, East Hanover, NJ.

This manuscript was presented in part at The North American Menopause Society (NAMS) 21st annual meeting, Chicago, IL, October 6-9, 2010.

Funding/support: This research was funded by Novartis Pharmaceuticals Corporation.

Financial disclosure/conflicts of interest: F. Laliberté, K. Dea, and P. Lefebvre are employees of Groupe d'analyse Ltée, which has received research grants from Novartis Pharmaceuticals Corporation. M.S. Duh is an employee of Analysis Group Inc., which has also received research grants from Novartis Pharmaceuticals Corporation. K.H. Kahler and M. Rolli are employees of Novartis Pharmaceuticals Corporation.

Address correspondence to: Patrick Lefebvre, MA, Groupe d‘analyse Ltée, 1000 rue de la Gauchetière Ouest, Bureau 1200, Montréal, Québec, Canada H3B 4W5. E-mail: plefebvre@analysisgroup.com

©2011The North American Menopause Society