BREAST CANCER RISK FACTORS
What do we know about breast
cancer risk factors?
There are no known definitive causes of most
breast cancers. However, epidemiologic studies have identified
some factors to be associated with a woman's risk for developing
breast cancer. Simply being a woman and getting older increases
a woman's risk for developing breast cancer, yet having one or
more of these factors does not necessarily mean one will develop
breast cancer.
Hormonal
Evidence suggests that the longer a woman is exposed to the hormone
estrogen (made by the body, taken as a drug, or delivered by a
patch), the more likely she is to develop breast cancer. Below
are hormonal factors related to breast cancer risk:
-
Early menarche (before age 13)
- Late menopause
(after age 55)
- Never having
given birth
- Having a
first born child at an older age (after age 30)
- Having never
breast fed a child
- Taking hormone
replacement therapy (5 or more years, possibly only if combined
estrogen and progesterone)
- Recent oral
contraceptive use
- Having taken
DES (diethylstilbestrol, a synthetic estrogen used between the
1940s and 1971) during pregnancy
- Obesity
after menopause (fat tissue, especially around the waist, can
change some hormones into estrogen)
- Personal
history of breast cancer. Previous breast cancer increases the
risk of developing cancer in the other breast.
Other
The following breast conditions are associated with an increased
risk for developing breast cancer:
-
Atypical hyperplasia
- Lobular
carcinoma in situ
- Higher breast
density. (The majority of breast cancer develops in the lobular
or ductal tissues, and a high proportion of lobular and ductal
tissue appears dense on mammograms making it more difficult to
see abnormalities in dense breast tissues.)
- Radiation
therapy. Exposure to high-dose ionizing radiation before age 30
is associated with an increased risk for developing breast cancer.
Known genetic factors explain only a small proportion (5-10%)
of breast cancer incidence. Yet those women with specific genetic
traits have a 50% to 80% chance of developing breast cancer in
their lifetime. Yet those women with specific genetic traits have
a 50% to 80% chance of developing breast cancer in their lifetime.
Inherited genetic factors include:
Family history
A woman's risk for developing breast cancer increases if her mother,
sister, or daughter had breast cancer, especially at a young age,
and is higher if more than one first-degree relative developed
cancer.
Breast cancer
gene mutations
Women with mutations in breast cancer 1 (BRCA1) and breast cancer
2 (BRCA2) genes tend to have cancers that occur at a younger age.
Damaged
Women with a damaged tumor prevention gene called p53 tend to
develop a breast cancer that is more aggressive.
Personal Risk Factors
Women with the following characteristics are at an increased risk
for breast cancer:
-
High socioeconomic status
- Urban residence
- Tall height
- Jewish heritage
- Excessive
alcohol consumption
The above risk factors have been determined by epidemiological
studies to increase a woman's chance of developing breast cancer.
However, it is important to note that having any of these risk
factors does not necessarily mean that one will develop breast
cancer. In fact, 70% of all breast cancer cases are found in women
who do not have any known risk factors. If you have any of these
risk factors or if you are concerned about your risk of developing
breast cancer, there are several practical steps you can take
to reduce your risk.
Protective Factors
These are characteristics that decrease one's
risk for developing breast cancer.
- Being physically active everyday
- Keeping off excess weight
- Breastfeeding
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