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Last Updated: Apr 16, 2008 - 5:52:06 PM |
WEDNESDAY April 9, 2008 (foodconsumer.org) -- Women who were treated with estrogen therapy had to face higher risk of breast disease than previously thought. A new study found those who took conjugated equine estrogen were more than twice as likely as those who took placebo to develop specific types of benign breast disease.
Conjugated equine estrogen is a commonly prescribed form of estrogen. The impact of estrogen on the risk of developing benign proliferative breast disease, which is associated with elevated risk of breast cancer, has been unclear. Some studies had been done, but the results were inconclusive.
The randomized controlled trial published online April 8 in the Journal of the National Cancer Institute involved 10,739 postmenopausal women with hysterectomy who participating in the Women's Health Initiative study. The women were either given conjugated equine estrogen or a placebo and followed for almost seven years.
Tom Rohan, M.D., Ph.D., of the Albert Einstein College of Medicine in New York and colleagues identified and examined non-cancerous breast biopsies in each of the trial arms. They found a total of 232 cases of benign proliferative breast disease with 155 among those who took estrogen supplements and 77 in the placebo group.
The results showed that the risk of developing benign disease was increased by more than two-fold in women taking conjugated equine estrogen compared with those taking a placebo.
"The prevailing hypothesis concerning the natural history of breast cancer is that benign proliferative breast disease without atypia, proliferative disease with atypia, and in situ cancer represent successive steps preceding the development of invasive breast [cancer]. In keeping with this hypothesis, women with benign proliferative breast disease have an increased risk of subsequent breast cancer," the authors wrote.
Early studies found a combinational hormone therapy with estrogen and progestin increased the risk of breast cancer and other life-threatening conditions. But this women's study did not show use of estrogen alone was not associated with increased incidence of breast cancer.
The results of this current study suggested that using estrogen alone may increase the risk of breast cancer later. Regardless, estrogen is a well established risk factor for certain types of breast cancer.
Some studies have showed that women with high levels of estrogen in the blood were more likely to have recurrence of breast cancer, suggesting use of estrogen alone is not safe.
One study published in the March 2008 issue of Cancer Epidemiology, Biomarkers and Prevention showed women who had breast cancer recurrence had twice as much of estrogen in their blood as that in women who remained cancer-free.
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