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Confirmed: breast Ca more likely in HRT users.

A prospective observational study that began following more than 50,000 California teachers in 1995 has confirmed reports linking hormone replacement therapy to breast cancer, but suggests obesity may offer some protection.

Data from 56,867 women enrolled in the California Teachers Study indicate that women who used estrogen therapy for at least 15 years had a 19% increase in breast cancer risk, and women who used combined estrogen-progestin therapy had an 83% increase in breast cancer risk.

The increase in risk was confined to tumors that were positive for both estrogen and progesterone receptors, wrote Tanmei Saxena, an MD/PhD student at the University of Southern California Keck School of Medicine, Los Angeles, and her coauthors. It was also more pronounced in women with low body mass index (BMI).

"These findings, taken in context of the larger literature on this topic, continue to underscore the need to personalize risk-benefit discussions for women contemplating the use of [hormone therapy]," they wrote (Cancer Epidemiol. Biomarkers Prev. 2010;19:OF1-13).

The California Teachers Study is a prospective cohort study of 133,479 women who were enrolled in 1995. For the purposes of this study, the investigators excluded women who were not California residents, who had a previous or unknown history of breast cancer, who were older than 80 years at baseline, who were premenopausal or of unknown menopausal status, or who had an unknown history of hormone therapy.

Of the remaining 56,867 perimenopausal and postmenopausal teachers, 2,857 women (5%) were diagnosed with pathologically confirmed invasive breast cancer through December 2006, after a mean follow-up of 9.8 years. The average age at diagnosis was 67.1 years.

Compared with women who never used any hormone therapy, those who did had a statistically significant 40% increase in the risk of breast cancer. The increase in risk was 19% for women who reported at least 15 years of estrogen-alone therapy, and 83% in women who reported at least 15 years of combined estrogen-progestin therapy.

Current use of hormonal therapy was associated with higher risk than past use. The greatest increase in risk--69%--was among women who were using estrogen-progestin therapy currently and had never used any other formulation.

The longer the women used hormone therapy, the greater the risk. The increase associated with duration of use was statistically significant for all forms of hormone therapy. The increase in risk was 42% for those using estrogen-progestin therapy for 3-5 years, 50% at 6-9 years, 67% at 10-14 years, 79% at 15-19 years, and 92% at 20 years or more.

BMI seemed to modify the risk associated with hormonal therapy, the investigators reported. In women with a BMI of 25 or less, the relative risk of breast cancer was 2.1 in current long-term users of estrogen and progestin, compared with women who had never used hormone therapy. In women with a BMI of 25-30, relative risk was 1.9 in current long-term users of estrogen and progestin. However, the effect was not statistically significant in women with a BMI over 30.

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Major Finding: Compared with women who have never used hormone replacement therapy, those who used estrogen therapy for 15 years or more had a 19% greater risk of breast cancer, and those who used combined estrogen-progestin therapy had an 83% greater risk.

Data Source: Prospective observational study of 56,867 perimenopausal and postmenopausal women participating in the California Teachers Study.

Disclosures: The National Cancer Institute and the California Breast Cancer Research Fund sponsored the study. A coauthor disclosed serving as an expert witness for plaintiffs pursuing Prempro litigation.

BY ROBERT FINN

FROM CANCER EPIDEMIOLOGY, BIOMARKERS AND PREVENTION
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Title Annotation:WOMEN'S HEALTH; hormone replacement therapy
Author:Finn, Robert
Publication:Internal Medicine News
Geographic Code:1USA
Date:Sep 1, 2010
Words:608
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