The Journal of Clinical Endocrinology & Metabolism Vol. 92, No. 2 0
Copyright © 2007 by The Endocrine Society
Patient Information Page from The Hormone Foundation |
Breast Cancer Prevention
Richard J. Santen, MD and
Rena V. Sellin, MD
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What is the relationship between hormones and breast cancer?
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Estrogen, the main female sex hormone, is produced mostly by the ovaries. It is responsible for a woman’s sexual development, including the growth of breasts and regulation of her menstrual cycle. At menopause (usually age 51) the ovaries stop producing estrogen but some is still produced in smaller amounts from pre-hormones made by the adrenal glands, which are then transformed into estrogen by fat tissue.
Estrogen travels through the blood stream and attaches to estrogen receptors on specific cells in your body. Breast tissue has these types of cells and is one of the main targets for estrogen. Estrogen stimulates the growth of breast cells. For example, pregnant women have higher estrogen levels that cause the breasts to get larger in preparation for breastfeeding. For this reason, if a woman develops cancer cells in her breast, estrogen can stimulate the growth of that cancer.
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Who is at risk for breast cancer?
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Breast cancer is one of the most common cancers in American women. Generally, women are at greater risk if they are older and/or overweight, and if they: - Started their period before age 12
- Reached menopause after age 55
- Never had children
- Delay pregnancy until after age 30
- Postmenopausal women on combination hormone therapy (estrogen plus progestin)
Women with a history of certain types of benign (noncancerous) breast disease are also at risk. These include lesions such as atypical ductal hyperplasia, atypical lobular hyperplasia and lobular carcinoma in situ (LCIS). They are usually found when a lump is found and a sample of the tissue is examined under a microscope (biopsy).
Also, having mutations of the BRCA1 or BRCA2 gene or a family history of breast cancer, especially in first-degree relatives such as your mother, sister or daughter increases your risk.
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How do I determine my risk of breast cancer?
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Your doctor can work with you to calculate your risk for developing breast cancer within five years and during your lifetime using a method called the Gail Model. This model takes into account the general risks for breast cancer (listed in the section above) and any breast lumps that you may have had biopsied in the past.
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How can you prevent breast cancer?
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You can lower your risk of developing breast cancer by adopting a healthy lifestyle that includes a well-balanced diet and regular exercise. You can also limit your exposure to estrogen by losing weight if overweight, and by avoiding outside sources of estrogen such as oral contraceptives ("the pill") or hormone replacement therapy.
If you are at high risk of developing breast cancer your doctor may recommend a class of drugs called selective estrogen receptor modulators (SERMs). Two drugs in particular have been effective in breast cancer prevention:
- Tamoxifen is approved by the U.S. Food and Drug Administration (FDA) for breast cancer prevention in pre-and in postmenopausal women (aged 35 and older) who are at high risk. Tamoxifen prevents estrogen from stimulating the growth of breast cells which could become cancerous.
- Raloxifene is approved by the FDA for the prevention and treatment of osteoporosis (brittle bones) in postmenopausal women (aged 51 and older). It has been shown to work as well as tamoxifen in reducing breast cancer risk in post-menopausal women but is not yet FDA approved for breast cancer prevention.
Tamoxifen and raloxifene only reduce the risk of breast cancer by 50%. The decision to take these medications always depends on the balance between the benefits and risk of side effects, which can include uterine cancer, stroke, and blood clots in the veins and lungs. Your doctor will work with you to find the best option for you.
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What should you do with this information?
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Every woman should do monthly breast self-exams and have yearly exams done by her doctor. If you are age 40 or older, or if you are younger and have a family history of breast or ovarian cancer, you should have an annual mammogram. Talk with your doctor about your level of risk for developing breast cancer and what you can do to prevent it.
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Resources:
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- Find-an-Endocrinologist: Visit www.hormone.org or call 1-800-HORMONE (1-800-467-6663)
- Breast Cancer Risk Assessment Tool: http://www.cancer.gov/bcrisktool/
- National Cancer Institute (NIH): www.cancer.gov
- Susan G. Komen Breast Cancer Foundation: http://www.komen.org
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Footnotes
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For more information on how to find an endocrinologist, download free publications, translate this fact sheet into other languages, or make a contribution to The Hormone Foundation, visit www.hormone.org/bilingual or call 1-800-HORMONE (1-800-467-6663). The Hormone Foundation, the public education affiliate of The Endocrine Society (www.endo-society.org), serves as a resource for the public by promoting the prevention, treatment, and cure of hormone-related conditions. This page may be reproduced non-commercially by health care professionals and health educators to share with patients and students.
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