| Causes and Risk Factors |
| Gender: While men also get the disease, it is about 100 times more common in women than in men |
| Age: Risk increases with age. About two-thirds of women with invasive breast cancer are 55 or older when the cancer is detected |
| Genetic risk factors: About 5-10% of breast cancers are thought to be linked to certain inherited gene mutations. Women with these genetic markers have up to an 80% chance of getting breast cancer during their lifetimes |
| Family history: Women whose close blood relatives have this disease have higher risk themselves. The relatives can be from either side of the family. Having a mother, sister or daughter with breast cancer roughly doubles a woman's risk. However, it's important to note that 70-80% of women who get breast cancer do not have any family history of this disease |
| Personal history of breast cancer: A woman who has already had breast cancer has a greater chance of getting a new incidence of breast cancer. This is different from a recurrence of the first cancer |
| Race: Caucasian women are slightly more likely to get breast cancer than African-American women, but African-American women are more likely to die of breast cancer. Part of the reason may be that African-American women tend to have faster growing tumors, though we don't know why. Asian, Hispanic and Native-American women have a lower risk of getting and dying from breast cancer |
| Dense breast tissue: Women with denser breast tissue have a higher risk of breast cancer. Dense breast tissue means there is more gland tissue and less fatty tissue, which can also make it more difficult for doctors to spot problems on mammograms |
| Certain benign breast issues: Women who have certain benign breast changes may have an increased risk of breast cancer |
| Menstrual periods: Women who have had more menstrual periods, and as a result have been exposed to more of the hormones estrogen and progesterone, have a slightly increased risk of breast cancer. Such women would include those who began menstruating before age 12 or who ceased menstruating after age 55 |
| Earlier breast radiation: Women who have had radiation treatment for other cancers in the chest area have a greatly increased risk of breast cancer. The risk from chest radiation is highest if the radiation was given during the teens, when the breasts were still developing |
| Treatment with DES: In the past, some pregnant women were given the drug DES (diethylstilbestrol) because it was thought to reduce the possibility of miscarriage. Recent studies have shown that these women (and daughters who were exposed to DES while in the womb) have a slightly increased risk of getting breast cancer |
| Not having children or having them later in life: Women who haven't had children, or those who had their first child after age 30, have a slightly higher risk of breast cancer. Having multiple pregnancies and having them at an early age reduces breast cancer risk. This may be because pregnancy lowers the total number of lifetime menstrual cycles |
| Recent use of birth control pills: Studies have found that women who use birth control pills have a slightly higher risk of breast cancer than women who have never used them. Once the use has stopped, the risk seems to dissipate, and after ten years, the risk more or less disappears |
| Using post-menopausal hormone therapy: Post-menopausal hormone therapy has been used to help relieve menopause symptoms and to help prevent osteoporosis. For women who still have a uterus, doctors most often prescribe estrogen and progesterone. Estrogen alone can increase the risk of cancer of the uterus, so progesterone is added to help prevent this |
| Not breastfeeding: Studies have shown breastfeeding slightly lowers breast cancer risk, especially if the breastfeeding lasts 1.5 to 2 years. This may be because breastfeeding lowers a woman's total number of menstrual periods |
| Alcohol: Alcohol use is linked to an increased risk of breast cancer. Women who have two or more drinks daily have about one-and-a-half times the risk of women who drink no alcohol |
| Being overweight or obese: Obesity is linked to increased risk of breast cancer, especially if the weight gain took place later in life. Extra fat around the waist also seems to indicate higher risk, but the link between weight and breast cancer risk is complex and studies have often achieved conflicting results |
| Lack of exercise: Studies suggest exercise reduces breast cancer risk. One study found that as little as one hour and 15 minutes to two-and-a-half hours of brisk walking per week reduced the risk by 18%. Walking ten hours a week reduced the risk a little more |
| Night Work: Some studies have indicated women who work night shifts have a higher risk of breast cancer. This is a fairly recent finding and more studies are being done to look at this |
