"What's my risk of breast cancer?" is a question many women ask their doctors. Doctors have tools to help estimate a woman's personal risk. Most women who get breast cancer have no known risk factors besides age. Many women with one or more risk factors never get breast cancer. So it's impossible to know who will actually get breast cancer.
Factors that affect a woman's risk of breast cancer include:
- Age. The strongest risk factor is age. Risk goes up as a woman gets older. Most women who get breast cancer are older than 50.
- Personal history of breast cancer. Women who have had breast cancer in one breast are more likely to get it in the other breast.
- Family history. Having a mother, sister, or daughter who has had breast cancer increases a woman's risk. The risk is higher if her family member got breast cancer before age 40. A woman’s risk also is increased if more than one family member on either her mother’s or father’s side of the family has had breast cancer.
- Inheriting certain harmful gene mutations. Here are some key points about genes and breast cancer:
- Inheriting changes to certain genes, such as BRCA1 and BRCA2, greatly increases the risk of breast cancer.
- Inherited genetic changes account for about 10 percent of all breast cancers.
- If you have a relative who has a harmful gene mutation, you may want to talk to a genetic counselor to learn more about your personal risk. You may also want to seek genetic counseling if your family history of cancer suggests a gene mutation.
- A woman known to carry a harmful gene mutation should talk to her doctor about ways to try to lower her breast cancer risk or find breast cancer early.
- Certain breast changes that are not cancer. Women who have certain types of abnormal breast changes, such as atypical hyperplasia, ductal carcinoma in situ, and lobular carcinoma in situ, have a higher risk. These changes are found during a breast biopsy.
- Breast tissue that is dense on mammogram. Women whose breasts have more dense tissue relative to fatty tissue have a higher risk than women of about the same age who have little or no dense breast tissue.
- Menstrual and reproductive history. Getting your first menstrual period before age 12 increases breast cancer risk. Reaching menopause after age 55 increases breast cancer risk. Never having children or having children after age 30 also increases risk. Women who have a first baby before age 20 have a lower risk.
- Taking the hormones estrogen and progestin. Using menopausal hormone therapy containing both estrogen and progestin for more than five years increases breast cancer risk. It's not clear whether estrogen-only therapy affects risk. Using birth control pills may slightly increase the risk of breast cancer in current users, but this risk returns to normal over time.
- Radiation therapy to the chest. Radiation therapy to the chest for the treatment of cancer increases breast cancer risk. Risk depends on the dose of radiation and age of treatment. The risk is highest for radiation treatment used during puberty.
- Body weight. The chance of getting breast cancer after menopause is higher in women who are overweight or obese.
- Drinking alcohol. The more alcohol a woman drinks, the greater her risk of breast cancer.
- Taking DES. The drug DES, or diethylstilbestrol (dye-ETH-uhl-stil-BES-trol), was given to some pregnant women in the United States between about 1940 and 1971 to prevent miscarriage. (It is no longer given to pregnant women.) Women who took DES during pregnancy may have a slightly increased risk of breast cancer.
- Physical activity. Women who are not physically active throughout life may have an increased risk of breast cancer. Strenuous exercise for more than four hours per week may help lower breast cancer risk. Also, being active can help women prevent overweight and obesity, which are known risk factors for breast cancer in women who have reached menopause.
- Breastfeeding. Women who breastfeed have a lower risk of breast cancer.
- Race. In the United States, white women have the highest breast cancer rates. Yet women of all races get breast cancer. African-American women are more likely to die from breast cancer than white women. One reason is that cancer is often found in African-American women at a later, more advanced stage, when it may be harder to treat.
Researchers continue to look for other factors that might affect a woman's risk of getting breast cancer. Factors that do not appear to affect a woman's breast cancer risk include:
- Breast implants
- Miscarriage or abortion
- Underarm deodorant and antiperspirants
- Smoking – Although neither smoking nor secondhand smoke has been shown to increase the risk of breast cancer, they do have other cancer-causing effects. Smoking is the number one risk factor for lung cancer.
If you're looking for ways to lower your breast cancer risk, focus your efforts on a healthy lifestyle. Wholesome and well-balanced meals and regular physical activity can help you to maintain a healthy weight. Limit alcohol to no more than one drink a day. Whether these steps will protect you from breast cancer is not certain. But living a healthy lifestyle is a cornerstone of disease prevention.