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Risk Factors
No one knows the exact causes of breast cancer. Doctors often cannot explain
why one woman develops breast cancer and another does not. They do know that
bumping, bruising, or touching the breast does not cause cancer. And breast
cancer is not contagious. You cannot "catch" it from another person.
Research has shown that women with certain
risk factors
are more likely than
others to develop breast cancer. A risk factor is something that may increase
the chance of developing a disease.
Studies have found the following risk factors for breast cancer:
-
Age: The chance of getting breast cancer goes up as a woman gets older. Most
cases of breast cancer occur in women over 60. This disease is not common
before
menopause.
-
Personal history of breast cancer: A woman who had breast cancer in one breast
has an increased risk of getting cancer in her other breast.
-
Family history: A woman's risk of breast cancer is higher if her mother,
sister, or daughter had breast cancer. The risk is higher if her family member
got breast cancer before age 40. Having other relatives with breast cancer (in
either her mother's or father's family) may also increase a woman's risk.
-
Certain breast changes: Some women have cells in the breast that look abnormal
under a microscope. Having certain types of abnormal cells
(atypical hyperplasia
and
lobular carcinoma in situ
[LCIS]) increases the risk of breast
cancer.
-
Gene
changes: Changes in certain genes increase the risk of breast cancer.
These genes include
BRCA1,
BRCA2,
and others. Tests can sometimes show the
presence of specific gene changes in families with many women who have had
breast cancer. Health care providers may suggest ways to try to reduce the risk
of breast cancer, or to improve the detection of this disease in women who have
these changes in their genes. NCI offers publications on gene testing.
-
Reproductive and menstrual history:
-
The older a woman is when she has her first child, the greater her chance of
breast cancer.
-
Women who had their first
menstrual period
before age 12 are at an increased
risk of breast cancer.
-
Women who went through menopause after age 55 are at an increased risk of
breast cancer.
-
Women who never had children are at an increased risk of breast cancer.
-
Women who take
menopausal hormone therapy
with
estrogen
plus
progestin
after
menopause also appear to have an increased risk of breast cancer.
-
Large, well-designed studies have shown no link between abortion or miscarriage
and breast cancer.
-
Race: Breast cancer is diagnosed more often in white women than Latina, Asian,
or African American women.
-
Radiation therapy
to the chest: Women who had radiation therapy to the chest
(including breasts) before age 30 are at an increased risk of breast cancer.
This includes women treated with radiation for
Hodgkin's lymphoma.
Studies show
that the younger a woman was when she received radiation treatment, the higher
her risk of breast cancer later in life.
-
Breast density: Breast tissue may be dense or fatty. Older women whose
mammograms
(breast
x-rays)
show more dense tissue are at increased risk of
breast cancer.
-
Taking
DES
(diethylstilbestrol): DES was given to some pregnant women in the
United States between about 1940 and 1971. (It is no longer given to pregnant
women.) Women who took DES during pregnancy may have a slightly increased risk
of breast cancer. The possible effects on their daughters are under study.
-
Being
overweight
or
obese
after menopause: The chance of getting breast cancer
after menopause is higher in women who are overweight or obese.
-
Lack of physical activity: Women who are physically inactive throughout life
may have an increased risk of breast cancer. Being active may help reduce risk
by preventing weight gain and obesity.
-
Drinking alcohol: Studies suggest that the more alcohol a woman drinks, the
greater her risk of breast cancer.
Other possible risk factors are under study. Researchers are studying the
effect of diet, physical activity, and genetics on breast cancer risk. They are
also studying whether certain substances in the environment can increase the
risk of breast cancer.
Many risk factors can be avoided. Others, such as family history, cannot be
avoided. Women can help protect themselves by staying away from known risk
factors whenever possible.
But it is also important to keep in mind that most women who have known risk
factors do not get breast cancer. Also, most women with breast cancer do not
have a family history of the disease. In fact, except for growing older, most
women with breast cancer have no clear risk factors.
If you think you may be at risk, you should discuss this concern with your
doctor. Your doctor may be able to suggest ways to reduce your risk and can
plan a schedule for checkups.
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Dictionary Terms
atypical hyperplasia (AY-TIP-ih-kul HY-per-PLAY-zhuh)
A benign (not cancer) condition in which cells look abnormal under a microscope and are increased in number.
BRCA1
A gene on chromosome 17 that normally helps to suppress cell growth. A person who inherits certain mutations (changes) in a BRCA1 gene has a higher risk of getting breast, ovarian, prostate, and other types of cancer.
BRCA2
A gene on chromosome 13 that normally helps to suppress cell growth. A person who inherits certain mutations (changes) in a BRCA2 gene has a higher risk of getting breast, ovarian, prostate, and other types of cancer.
DES
A synthetic form of the hormone estrogen that was prescribed to pregnant women between about 1940 and 1971 because it was thought to prevent miscarriages. DES may increase the risk of uterine, ovarian, or breast cancer in women who took it. It also has been linked to an increased risk of clear cell carcinoma of the vagina or cervix in daughters exposed to DES before birth. Also called diethylstilbestrol.
estrogen (ES-truh-jin)
A type of hormone made by the body that helps develop and maintain female sex characteristics and the growth of long bones. Estrogens can also be made in the laboratory. They may be used as a type of birth control and to treat symptoms of menopause, menstrual disorders, osteoporosis, and other conditions.
lobular carcinoma in situ (LAH-byuh-ler KAR-sih-NOH-muh in SY-too)
A condition in which abnormal cells are found in the lobules of the breast. Lobular carcinoma in situ seldom becomes invasive cancer; however, having it in one breast increases the risk of developing breast cancer in either breast. Also called LCIS.
mammogram (MAM-o-gram)
An x-ray of the breast.
menopausal hormone therapy (MEH-nuh-PAW-zul HOR-mone THAYR-uh-pee)
Hormones (estrogen, progesterone, or both) given to women after menopause to replace the hormones no longer produced by the ovaries. Also called hormone replacement therapy and HRT.
menopause (MEH-nuh-PAWZ)
The time of life when a woman’s ovaries stop working and menstrual periods stop. Natural menopause usually occurs around age 50. A woman is said to be in menopause when she hasn’t had a period for 12 months in a row. Symptoms of menopause include hot flashes, mood swings, night sweats, vaginal dryness, trouble concentrating, and infertility.
menstrual period (MEN-stroo-al PEER-ee-od)
The periodic discharge of blood and tissue from the uterus. From puberty until menopause, menstruation occurs about every 28 days, but does not occur during pregnancy.
obese
Having an abnormally high, unhealthy amount of body fat.
overweight
Being too heavy for one’s height. Excess body weight can come from fat, muscle, bone, and/or water retention. Being overweight does not always mean being obese.
progestin (pro-JES-tin)
Any natural or laboratory-made substance that has some or all of the biologic effects of progesterone, a female hormone.
risk factor
Something that may increase the chance of developing a disease. Some examples of risk factors for cancer include age, a family history of certain cancers, use of tobacco products, certain eating habits, obesity, lack of exercise, exposure to radiation or other cancer-causing agents, and certain genetic changes.
x-ray
A type of high-energy radiation. In low doses, x-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, x-rays are used to treat cancer.
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