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There is no sure way to prevent breast cancer. But a woman might reduce
her risk somewhat by changing those risk factors that can be changed
(see the section, "What Are the Risk Factors for Breast Cancer?"). If
you avoid alcohol, exercise regularly, and maintain a healthy body
weight, you are decreasing your risk of getting breast cancer.
Breast-feeding for several months also seems to reduce breast cancer
risk. Likewise, not using PHT will avoid increasing your risk.
Other than these lifestyle changes, the most important action
a woman
can take is to follow early detection guidelines. Following the
American Cancer Society's guidelines for early detection (outlined in
the section, "Can
Breast Cancer Be Found Early?") will not prevent
breast cancer, but it can help find cancers when the likelihood of
successful treatment is greatest.
For Women Who Are or May Be at Increased
Risk
If you are a woman with a strong family history of breast
cancer, with
a known genetic mutation of a BRCA gene, or if you have had DCIS, LCIS,
or biopsies that have shown pre-cancerous changes, there may be some
additional things you can do to reduce your chances of developing
breast cancer.
Genetic Testing for BRCA Gene Mutations
While many women have relatives affected by breast cancer, in
most
cases this is not the result of BRCA gene mutations. Genetic testing
for these mutations can be complicated and expensive and can have a
wide range of consequences that need to be considered. Therefore it
should only be done when there is a reasonable suspicion that a
mutation may be present. Genetic counseling is strongly recommended
before any testing is done. (For more information, see the separate
American Cancer Society document, Genetic Testing: What You
Need to
Know.)
Recently the US Preventive Services Task Force recommended
that only
women with a strong family history be evaluated for genetic testing for
BRCA mutations. This group represents only about 2% of adult women in
the United States.
Women who are not of Ashkenazi (Eastern European) Jewish
heritage
should be referred for genetic evaluation if they have any of the
following:
- two first-degree relatives (mother, sisters, daughters)
with breast
cancer, one of whom was diagnosed when they were younger than
50
- three or more first- or second-degree relatives (includes
grandmothers, aunts, cousins) diagnosed with breast cancer
- both breast and ovarian cancer among first- and
second-degree
relatives
- a first-degree relative diagnosed with cancer in both
breasts
- two or more first- or second-degree relatives diagnosed
with ovarian
cancer
- a male relative with breast cancer
Women of Ashkenazi (Eastern European) Jewish heritage should be
referred for genetic evaluation if they have:
- a first-degree relative with breast or ovarian
cancer
- two
second-degree relatives on the same side of the family with breast or
ovarian cancer
Breast Cancer Chemoprevention
Chemoprevention is the use of drugs to reduce the risk of
cancer.
Several drugs have been studied for use in lowering breast cancer risk.
Tamoxifen: Tamoxifen
is a drug that blocks some of the effects of
estrogen on breast tissue. It has already been used for many years to
reduce the risk of recurrence in localized breast cancer and as a
treatment for advanced breast cancer (see the section, "How
Is Breast
Cancer Treated?"). Several studies have found that tamoxifen
can also
lower the risk of getting breast cancer in women known to be at
increased risk for the disease.
Results from the Breast Cancer Prevention Trial (BCPT) have
shown that
women at increased risk for breast cancer are less likely to develop
the disease if they take tamoxifen. Women in the study were assigned to
take either tamoxifen or a placebo pill for 5 years. After 7 years of
follow-up, women taking tamoxifen had 42% fewer breast cancers than
women who took the placebo, although there was no difference in the
risk of death due to breast cancer. Thus far, tamoxifen is the only
drug approved for use in reducing breast cancer risk in high-risk
women.
Because tamoxifen has side effects that include increased
risks of
endometrial (uterine) cancer and blood clotting, women should consider
the possible benefits and risks of tamoxifen before deciding whether or
not it is right for them.
If you are going to be taking tamoxifen because you have been
found to
have a BRCA mutation, it is important to know if your mutation is in
the BRCA1 or BRCA2 gene. BRCA1-related cancers may not be prevented by
tamoxifen.
Raloxifene:
Like tamoxifen, raloxifene also blocks the effect of
estrogen on breast tissue. A study comparing the effectiveness of the 2
drugs, called the Study of Tamoxifen and Raloxifene (STAR) trial, found
that raloxifene reduced the risk of invasive breast cancer to the same
degree as tamoxifen, although it didn't have the same protective effect
against non-invasive cancer (DCIS or LCIS). Raloxifene did, however,
have lower risks of certain side effects such as uterine cancer and
blood clots in the legs or lungs, compared to tamoxifen (although the risk of blood clots was still higher than normal).
Raloxifene is approved to help reduce breast cancer risk in women past menopause who have osteoporosis (bone thinning) or are at high risk for breast cancer.
Aromatase
inhibitors: Drugs such as anastrozole, letrozole, and
exemestane are also being studied as breast cancer chemopreventive
agents in post-menopausal women. These drugs are already being used to
help prevent breast cancer recurrences. They work by blocking the
production of small amounts of estrogen that post-menopausal women
normally make. But they can also have side effects, such as causing
joint pain and stiffness and bone loss, leading to a higher risk of
osteoporosis. None of these drugs is approved for reducing breast
cancer risk at this time.
Other drugs:
New studies are under way using other drugs as well. Some
studies have found that women who take aspirin or non-steroidal
anti-inflammatory drugs (NSAIDs) such as ibuprofen seem to have a lower
risk of breast cancer. Similar drugs (called COX-2 inhibitors) are
being tested to see if they can reduce the risk of breast cancer in
women who are at a high risk for this disease, although recent studies
have shown that these drugs can raise the risk of heart attacks. None
of these drugs is approved for reducing breast cancer risk at this
time.
Many of the drugs mentioned above are discussed further in the
section, "How
Is Breast Cancer Treated?", under hormonal treatment. For
more
information on the possible benefits and risks of chemopreventive drugs
see the separate American Cancer Society document, Medicines
to Reduce
Breast Cancer Risk.
Preventive Surgery for Women With Very High Breast Cancer Risk
For the few women who are at very high risk for breast cancer,
prophylactic surgery such as bilateral (double) mastectomy may be an
option.
Preventive
(prophylactic) mastectomy: This surgery can greatly
reduce
(but not eliminate) the risk of breast cancer by removing both breasts
before cancer is diagnosed. Some of the reasons for considering this
type of surgery may include:
- mutated BRCA genes found by genetic testing
- previous cancer in one
breast
- strong family history (breast cancer in several close
relatives)
- biopsy specimens showing lobular carcinoma in situ (LCIS)
There is no way to know ahead of time whether this surgery
will benefit
a particular woman. Some women with BRCA mutations will develop a fatal
breast cancer early in life, and a prophylactic mastectomy before the
cancer occurs might add many years to their lives. But while most women
with BRCA mutations develop breast cancer, some don't. These women
would not benefit from the surgery, although they would still have to
deal with its after effects.
While this operation removes nearly all of the breast tissue,
a small
amount remains. So although this operation markedly reduces the risk of
breast cancer, a cancer can still develop in the breast tissue
remaining after surgery. To date, this has been a rare problem.
Second opinions are strongly recommended before any woman
makes the
decision to have this surgery. The American Cancer Society Board of
Directors has stated that "only very strong clinical and/or pathologic
indications warrant doing this type of preventive operation."
Nonetheless, after careful consideration, this might be the right
choice for some women.
Prophylactic
oophorectomy (ovary removal): Women with a BRCA mutation
who have their ovaries surgically removed may reduce their risk of
breast cancer by 50% or more. This is because the surgery removes the
main sources (the ovaries) of estrogen in the body.
Although this document is not about ovarian cancer, it is
important
that women with a BRCA mutation recognize they also have a high risk of
developing ovarian cancer. Most doctors recommend that these women have
their ovaries surgically removed once child bearing is complete.
Revised: 09/13/2007
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