While we do not yet know exactly what causes breast cancer, we do know that certain risk factors are linked to the disease. A risk factor is something that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, such as smoking, drinking, and diet are linked to things a person does. Others, like a person's age, race, or family history, can’t be changed.
But risk factors don’t tell us everything. Having a risk factor, or even several, doesn’t mean that a woman will get breast cancer. Some women who have one or more risk factors never get the disease. And most women who do get breast cancer don't have any risk factors (other than being a woman and growing older). Some risk factors have a bigger effect than others, and your risk for breast cancer can change over time because of aging or lifestyle changes.
Although many risk factors may increase your chance of having breast cancer, it is not yet known just how some of these risk factors cause cells to become cancer. Hormones seem to play a role in many cases of breast cancer, but just how this happens is not fully understood.
Risk factors you cannot change
- Gender: Breast cancer is much more common in women than in men.
- Age: risk goes up with age.
- Genetic risk factors: Inherited changes (mutations) in certain genes like BRCA1 and BRCA2 can increase the risk.
- Family history: Breast cancer risk is higher among women whose close blood relatives have this disease.
- Personal history of breast cancer: A woman with cancer in one breast has a greater chance of getting another breast cancer (this is different from a return of the first cancer).
- Race: Overall, white women are slightly more likely to get breast cancer than African-American women. African-American women, though, are more likely to die of breast cancer.
- Dense breast tissue: Dense breast tissue means there is more gland tissue and less fatty tissue. Women with denser breast tissue have a higher risk of breast cancer.
- Certain benign (not cancer) breast problems: Women who have certain benign breast changes may have an increased risk of breast cancer. Some of these are more closely linked to breast cancer risk than others. For more details about these, see Non-cancerous Breast Conditions.
- Lobular carcinoma in situ: In this condition, cells that look like cancer cells are in the milk-making glands (lobules), but do not grow through the wall of the lobules and cannot spread to other parts of the body. It is not a true cancer or pre-cancer, but having LCIS increases a woman's risk of getting cancer in either breast later.
- Menstrual periods: Women who began having periods early (before age 12) or who went through menopause (stopped having periods) after the age of 55 have a slightly increased risk of breast cancer.
- Breast radiation early in life: Women who have had radiation treatment to the chest area (as treatment for another cancer) as a child or young adult have a greatly increased risk of breast cancer.
- Treatment with DES: Women who were given the drug DES (diethylstilbestrol) during pregnancy have a slightly increased risk of getting breast cancer. For more information on DES see DES Exposure: Questions and Answers.
Breast cancer risk and lifestyle choices
- Not having children or having them later in life: Women who have not had children, or who had their first child after age 30, have a slightly higher risk of breast cancer. Being pregnant many times or pregnant when younger reduces breast cancer risk.
- Certain kinds of birth control: Studies have found that women who are using birth control pills or an injectable form of birth control called depot-medroxyprogesterone acetate (DMPA or Depo-Provera®) have a slightly greater risk of breast cancer than women who have never used them. This risk seems to go back to normal over time once the pills are stopped.
- Using hormone therapy after menopause: Taking estrogen and progesterone after menopause (sometimes called combined hormone therapy) increases the risk of getting breast cancer. This risk seems to go back to normal over time once the hormones are stopped. For more information about this, see Menopausal Hormone Therapy.
- Not breastfeeding: Some studies have shown that breastfeeding slightly lowers breast cancer risk, especially if breastfeeding lasts 1½ to 2 years.
- Alcohol: The use of alcohol is clearly linked to an increased risk of getting breast cancer. Even as little as one drink a day can increase risk.
- Being overweight or obese: Being overweight or obese after menopause (or because of weight gain that took place as an adult) is linked to a higher risk of breast cancer.
Risk factors that are less clear or have been disproven
- Tobacco smoke: Smoking may increase the risk of breast cancer. The increased risk seems to affect certain groups, such as women who started smoking before they had their first child.
- Night work: A few studies have suggested that women who work at night (nurses on the night shift, for instance) have a higher risk of breast cancer.
Certain factors have been studied without finding a link to breast cancer:
- Induced abortions (see Is Abortion Linked to Breast Cancer?)
- Breast implants: These may be linked to a rare type of lymphoma, though
- Chemicals: At this time research does not show a clear link between breast cancer risk and exposure to things like plastics, certain cosmetics and personal care products, and pesticides (such as DDE). Research is being done on the possible health effects of these and similar compounds.
Our detailed guide Breast Cancer has more information about these risk factors.
Last Revised: 01/14/2016