Hormone Therapy and the Risks of Breast and Endometrial Cancers
Your risk of developing breast cancer
increases slowly as you age, especially after age 50. Of American women who
live to age 80, about 1 in 8 will be diagnosed with breast cancer at
some point in her life.1 Taking
progestin (hormone replacement therapy, or HRT) may increase that risk. Taking estrogen alone may slightly
increase breast cancer risk. Large studies have shown either a slight risk
increase or none at all.2, 3
These average increased breast cancer risks are
relatively low for the general population of postmenopausal women. But your
personal risk that hormone therapy will stimulate cancerous cell growth may be
significantly lower or higher, depending on your risk factors. For more
information about breast cancer risk factors, see the topic Breast Cancer.
When you're first diagnosed with breast cancer, all you can
think about is "Am I going to die?" But as you begin to learn to live
with your cancer diagnosis, you start to think about other
things, like "What am I going to look like bald?" It may sound
frivolous, but ask any breast cancer survivor and she'll tell you that she
thought a lot about whether to splurge on that real human hair wig or
what she'd look like in a swimsuit.
Feeling good about how you look is an important part of feeling...
In the United States,
endometrial (uterine) cancer is the most common cancer
of the lower female genital tract. Women with an intact uterus who take
estrogen therapy without progestin increase their risk of endometrial cancer.
Adding progestin protects the uterus from this risk.
Weighing cancer risks for women who still have a uterus
Taking only estrogen
(estrogen replacement therapy, ERT) after menopause increases your risk of
Taking progestin along with estrogen (HRT) eliminates the slightly higher risk of endometrial cancer
that is linked to estrogen-only therapy. (Estrogen-only therapy stimulates
overgrowth of the uterine lining, which can become cancerous. Progestin
regulates that growth.)
Although adding progestin protects your
uterus, it increases breast cancer risk. The British Million Women Study
researchers have found that, among women ages 50 to 64, long-term (10-year) HRT after menopause causes more breast cancers than long-term estrogen replacement therapy (19 out of 1,000 versus 5
out of 1,000).2Women's Health Initiative
researchers have similarly found that out of 10,000 women taking HRT for longer than 5 years there were 4 to 6 more cases of breast cancer per year than women who did not take HRT.4
Unanswered questions about short-term and low-dose hormone therapy
Using hormone therapy for a short time just after
menopause is hoped to be low-risk. Some studies have suggested that short-term
use of hormone therapy (up to 4 years) may not increase breast cancer
risk.5 More study is needed
to see how much lower-dose and shorter-term HRT and ERT reduce the risks of
using long-term hormone replacement, including risks of breast and
gynecological cancers, cardiovascular disease, and
National Cancer Institute (2006). Probability of
breast cancer in American women. National Cancer Institute Fact Sheet. Available online:
Million Women Study Collaborators (2003). Breast
cancer and hormone-replacement therapy in the Million Women Study.
Lancet, 362(9382): 419-427.
Women's Health Initiative Steering Committee (2004).
Effects of conjugated equine estrogen in postmenopausal women with
hysterectomy. JAMA, 291(14): 1701-1712.
North American Menopause Society (2010). Estrogen and
progestogen use in postmenopausal women: 2010 position statement of the
North American Menopause Society. Menopause, 17(2):
242-255. Also available online: http://www.menopause.org/PSht10.pdf.
Lobo RA (2007). Menopause: Endocrinology, consequences
of estrogen deficiency, effects of hormone replacement therapy, treatment
regimens. In VL Katz et al., eds., Comprehensive Gynecology, 5th ed., pp. 915-931. Philadelphia: Mosby
Primary Medical Reviewer
Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer
Carla J. Herman, MD, MPH - Geriatric Medicine
May 4, 2010
WebMD Medical Reference from Healthwise
May 04, 2010
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