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The BCERF program on the Cancer Risks of Environmental Chemicals in the Home and Workplace closed on March 31, 2010. No further updates will be made to this web site. Please go Cornell University’s eCommons web site to access BCERF’s archived research and educational materials (http://ecommons.library.cornell.edu/handle/1813/14300).

Hormones and the Risk of Breast Cancer
Frequently Asked Questions

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Does hormone replacement therapy increase breast cancer risk?

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Women who use postmenopausal hormone treatment (hormone replacement therapy) have a higher risk of breast cancer than women who do not use this treatment. The risk depends on which hormones are taken and for how long.

Studies examining the currently used treatments containing estrogen and progesterone have reported a 6% to 8% increase in breast cancer risk for each year of use relative to women not receiving treatment. Earlier studies examining estrogen only treatment reported that breast cancer risk returned to normal 5 years after stopping treatment. Please see Fact Sheet #40 Hormone Treatments and the Risk of Breast Cancer for more information.

Answered by: Barbour Warren, Ph.D.

Last Reviewed: 08.14.06

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