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For decades, women have used hormone replacement therapy (HRT,
also known as post-menopausal
hormone therapy) to ease symptoms of menopause, such as
hot flashes. Many doctors and their patients believed HRT had other
health benefits, too. But studies have led doctors to question some of
these beliefs.
Here we will discuss what is known about how HRT can affect a
woman's risk of getting certain cancers. We will not go into the
possible effects of HRT on other diseases, such as osteoporosis (bone
thinning), heart disease, and dementia.
This is not meant to be a policy statement of the American
Cancer Society -- it is a summary of published medical studies on the
subject. Women who are thinking about using HRT should talk with their
doctors about the information covered here. Woman should also
understand the risks and benefits of HRT and the follow-up they will
need if HRT is used. Based on this information, a woman and her doctor
may decide that hormones are or are not needed for a period of time to
help with symptoms of menopause.
Menopause, symptoms, and hormone replacement
therapy
Menopause is the time in a woman's life when her ovaries stop
releasing eggs and start making smaller amounts of the 2 main female
hormones, estrogen and progesterone. Over time, this causes menstrual
periods to stop. Women who have their ovaries removed by surgery
(oophorectomy) or whose ovaries stop working for other reasons go
through menopause, too, but much more suddenly.
Lowered hormone levels cause the symptoms that are often
linked to menopause -- hot flashes and night sweats, for instance.
These symptoms tend to fade away at some point, whether or not they are
treated. Other symptoms, like dryness and thinning of vaginal tissues
can start later and may get worse over time. Low estrogen levels also
increase a woman's risk of other health problems, such as osteoporosis.
Types of hormone replacement therapy
The term hormone replacement therapy (HRT) is used to mean
estrogen and progestin, or estrogen alone, given to a woman whose
levels of these hormones are low because of menopause.
Estrogen replacement therapy (ERT)
Estrogen replacement therapy is used to raise estrogen levels
in the body. CEE (conjugated equine estrogens) forms of ERT (such as
Premarin®) are most common and have been used for the longest
time.
Combined hormone replacement therapy
Combined HRT uses both estrogen and progestin
(progesterone-like hormone). Combined HRT can be given 2 ways:
- Continuous
HRT means giving the same dose of estrogen and progestin each day.
- Sequential
(cyclical) HRT uses different amounts of the hormones during the month
so that it is more like the natural menstrual cycle.
ERT and combined HRT are sometimes used to relieve symptoms of
menopause. Some doctors believe hormone therapy can also lower a
woman's risk of some other health problems linked to low estrogen
levels. The increased risk of hormone replacement therapy is the same
for "bioidentical" and "natural" hormones as it is for "synthetic"
hormones.
How hormone replacement therapy is given
Both ERT and combined HRT can be given as a systemic therapy.
This means that the hormones are given as pills or as a patch. They are
absorbed through the digestive system or the skin and reach all parts
of the body through the bloodstream.
As another option, hormone treatments may be used topically. This
means they mainly reach nearby areas rather than the whole body.
Hormones that are placed in the vagina can enter the bloodstream, but
the amount that gets in depends on the type of hormone and the dose.
Dry or thinned vaginal tissues respond to very small doses of estrogen.
These smaller doses are placed inside the vagina in the form of creams,
rings, or tablets that slowly release hormones to the vagina and nearby
tissues. Even though tiny amounts of hormone may enter the blood, most
of it stays in the vaginal tissues. This is considered topical use.
Hormone replacement therapy and cancer risk
Several large studies have looked at the possible links between hormone replacement therapy and different types of cancer.
Hormone replacement therapy and endometrial
(uterine) cancer risk
Estrogen replacement therapy (ERT)
Using systemic ERT as a pill or patch increases a woman's risk
of endometrial cancer (cancer of the lining of the uterus). Long-term
use of vaginal creams, rings, or tablets containing estrogen may also
increase the levels of estrogen in the body. The risk remains higher
than average even after ERT is no longer used.
Because of this, estrogen alone is almost never given to women
who have gone through menopause and who still have a uterus.
Combined hormone replacement therapy (HRT)
Studies show that combined HRT (progestin and estrogen) may
help menopause symptoms in women who still have a uterus without
increasing their risk of endometrial cancer.
One study showed that about 1 in 9 women treated with only
estrogen for 3 years developed a type of pre-cancerous change in their
endometrium called
atypical hyperplasia. Women treated with both types of
hormones did not develop this change any more often than women not
taking any hormones.
The Women's Health Initiative (WHI), a large, randomized trial
of women getting either continuous combined HRT or a placebo (an
inactive substance used for comparison, also known as a "sugar pill")
also found that combined HRT did not increase endometrial cancer risk.
But more of the women getting HRT had abnormal vaginal bleeding (a
possible sign of endometrial cancer) that needed further testing.
A woman who has had her uterus removed (hysterectomy) is not
in danger of developing endometrial cancer, regardless of whether she
takes ERT or combined HRT. But because the only reason for giving
progestin is to protect the endometrium, a woman without a uterus would
most likely be given ERT alone.
Hormone replacement therapy and breast
cancer risk
Combined hormone replacement therapy (HRT)
Results from the Women's Health Initiative (WHI) have shown
that daily use of combined HRT increases a woman's chance of developing
breast cancer by about 5% to 6% with each year of use. If 10,000 women
took combined HRT for a year, this would add up to about 8 more cases
of breast cancer per year than if they had not taken HRT. The longer
HRT was used, the more the risk increased.
In this study, women who took combined HRT also had a higher
risk of having breast cancer detected at a more advanced stage and were
more likely to have breast changes seen on mammograms.
But there are still questions about combined HRT and breast
cancer risk. Most of the increased risk of breast cancer from combined
HRT is thought to be due to the progestin. Doctors are now looking at
whether the dose of progestin can be decreased to lower the risk of
breast cancer, but still protect the endometrium.
Women who have had a hysterectomy should take ERT instead of
combined HRT. These women do not need progestin to protect against
uterine cancer and are increasing their risk of breast cancer by taking
combined HRT.
HRT risks apply only to current and recent users. A woman's
breast cancer risk is thought to decrease after she stops HRT and
return to that of the general population (the usual risk) within 3
years of stopping.
Estrogen replacement therapy (ERT)
Part of the WHI looked at women who had had a hysterectomy,
and whose ovaries were either removed or had stopped working. Those who
were taking only estrogens did not have an increased risk of breast
cancer.
The British "Million Women Study," and many other studies like
this, reported a very slight increase in breast cancer risk (about 1%
to 3% increase per each year of use) among women who took ERT.
Hormone replacement therapy and ovarian
cancer risk
Ovarian cancer is rare, which makes it harder to study its
risk factors. Even when something increases the relative risk (or
probability) of developing ovarian cancer, a woman's absolute risk is
still likely to be low. For example, a woman is much more likely to be
affected by a 50% increase in her risk for breast cancer than by a 50%
increase in her risk for ovarian cancer, because her risk for ovarian
cancer is much lower to begin with.
To put this another way, in a group of 100 women with a 12%
lifetime risk of breast cancer and a 2% risk of ovarian cancer, you
would expect about 2 cases of ovarian cancer and 12 breast cancers. A
50% risk increase in both cancers would mean there would be 18 women
with breast cancer but only 3 with ovarian. So each woman's absolute
risk of ovarian cancer would still be much lower than her risk of
breast cancer.
Estrogen replacement therapy (ERT)
Studies have shown that women who take ERT have a higher risk
for ovarian cancer compared with women who take no hormones after
menopause. The risk of ovarian cancer increases the longer a woman uses
ERT. The largest study so far found that women who had used ERT for 5
or more years had about a 50% increased risk of developing ovarian
cancer.
Combined hormone replacement therapy (HRT)
It's still not known for certain if HRT increases the risk of
ovarian cancer. The WHI study found that continuous combined HRT may
increase the risk of ovarian cancer slightly. But this finding may have
been due to chance because of the small number of women who developed
ovarian cancer during the study. Other studies also suggest that HRT
may increase risk slightly, although less than ERT does.
Hormone replacement therapy and colorectal
cancer risk
Combined hormone replacement therapy (HRT)
The WHI study found that combined HRT reduced the risk of
colorectal cancer by about 40%. This effect seemed to fade when the
women were checked a little more than 2 years after the HRT was
stopped. This risk reduction has also been found in other studies. Of
course, these results must be weighed along with the effects of HRT on
the risk of other types of cancer, as well as its effects on
non-cancerous conditions.
Estrogen replacement therapy (ERT)
In the WHI group that took estrogen only, estrogen replacement
therapy did not seem to have any effect on the risk of colorectal
cancer. Other studies have found a slightly lower risk of colorectal
cancer in women who have used ERT for many years.
Hormone replacement therapy and lung cancer risk
Combined hormone replacement therapy (HRT)
The WHI study found that after about 5 years of combined HRT use and
another 3 years of follow-up off the drugs, women who took HRT had an
increased risk of dying from lung cancer, especially non-small cell lung cancer.
However, the risk of developing lung cancer was not significantly higher in women
taking HRT than in the women who took the placebo. Some other, less rigorous
studies have also looked at a possible link between combined HRT and the risk
of getting lung cancer, but the results have been mixed.
Smoking is by far the most important cause of lung cancer. It is not clear if
using combined HRT might somehow increase the chance of lung tumors
forming, or if it might cause small, existing tumors to grow faster. But because
it appears to raise the risk of dying from lung cancer, women who are at
increased risk for lung cancer, such as smokers and former smokers, should
discuss these results with their doctor when deciding whether to start or continue
taking combined HRT.
Estrogen replacement therapy (ERT)
Researchers in charge of the WHI study are now looking to see if there is a
link between ERT and the risk of developing or dying from lung cancer, but they
have not published these study results yet.
What does it all mean?
The decision to use hormone replacement therapy, either
estrogen replacement therapy (ERT) or combined hormone replacement
therapy (HRT), after menopause should be made by each woman and her
doctor after weighing the possible risks and benefits. Things to think
about include
- the risk of breast, endometrial, ovarian, and lung cancer
- the risks of other serious conditions affected by HRT that
are not covered here, such as heart disease, stroke, and serious blood
clots (DVT or deep vein thrombosis)
- other medicines that may be used to treat menopausal
symptoms or osteoporosis.
Other factors to consider include how bad the woman's
menopausal symptoms are and the type and dose of the hormones the
doctor recommends.
If a woman and her doctor decide that ERT or combined HRT is
the best treatment for certain symptoms of menopause or health
problems, it is usually best to use it at the lowest dose that works
for her and for as short a time as possible. Other treatments for these
symptoms and conditions should also be considered.
It is important that any woman taking ERT or combined HRT be
checked yearly by her doctor for any signs of cancer.
All women should report any vaginal bleeding that happens
after menopause to their doctors right away -- it may be a sign of
endometrial cancer.
Women should follow the American Cancer Society guidelines for
cancer early detection, especially those for breast cancer. These
guidelines are in Breast Cancer: Early Detection.
Adding progestin to estrogen (combined HRT) reduces the risk
of endometrial cancer, but may not eliminate it entirely. If you are
using vaginal cream, rings, or tablets containing estrogen talk to your
doctor about follow-up and the possible need for progestin treatment.
For women who have had a hysterectomy (removal of the uterus),
progestin does not need to be added because there is no risk of
endometrial cancer. Adding progestin does not protect against breast
cancer and, in fact, raises the risk further, so ERT is a better
option.
In recent years, many over-the-counter "natural" products have
been marketed to help with menopausal symptoms. These include certain
vitamins, soy-based products, and herbal products (such as black cohosh
and red clover). These products are considered dietary supplements (as
opposed to drugs) and have not been evaluated by the Food and Drug
Administration (FDA) for their safety or effectiveness. Some of the
products have been tested, mostly in small clinical trials, but many of
the tests had problems with the way they were done that could affect
their outcomes. Well-controlled scientific studies are needed to help
find out if these products work and if they are any safer than the HRT
drugs now in use. You can learn more from reading How to Know What Is Safe:
Choosing and Using Dietary Supplements.
Additional resources
National organizations and Web sites*
Food and Drug
Administration (FDA)
Toll-free number: 1-888-463-6332
Web site: www.fda.gov
For information on menopause in English and Spanish: www.fda.gov/ForConsumers/ByAudience/ForWomen/Women'sHealthTopics/ucm117978.htm
National Cancer
Institute
Toll-free number: 1-800-422-6237 (1-800-4-CANCER)
Web site: www.cancer.gov
Menopausal Hormone Replacement Therapy page: www.cancer.gov/clinicaltrials/digest-postmenopausal-hormone-use
National
Institutes of Health
Telephone number: 301-496-4000
Web site: www.nih.gov
Menopausal Hormone Therapy Information page: www.nih.gov/PHTindex.htm
National Women's
Health Information Center
Toll-free number: 1-800-994-9662 (1-800-994-WOMAN)
Web site: www.womenshealth.gov
Menopause & Hormone Therapy page: www.womenshealth.gov/Menopause
*Inclusion on
this list does not imply endorsement by the American Cancer Society.
No matter who you are, we can help. Contact us anytime, day or
night, for information and support. Call us at 1-800-227-2345 or
visit www.cancer.org.
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Last Medical Review: 09/10/2009
Last Revised: 10/09/2009
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