Risk factors are conditions or agents that increase a person's chances of getting a disease. Here are the most common risk factors for breast cancer. - Personal and family history. A personal history of breast cancer or breast cancer among one or more of your close relatives, such as a sister, mother, or daughter.  - Estrogen levels in the body. High estrogen levels over a long time may increase the risk of breast cancer. Estrogen levels are highest during the years a woman is menstruating.  - Never being pregnant or having your first child in your mid-30s or later.  - Early menstruation. Having your first menstrual period before age 12.  -  Breast density. Women with very dense breasts have a higher risk of breast cancer than women with low or normal breast density.   -  Combination hormone replacement therapy/Hormone therapy. Estrogen, progestin, or both may be given to replace the estrogen no longer made by the ovaries in postmenopausal women or women who have had their ovaries removed. This is called hormone replacement therapy. (HRT) or hormone therapy (HT). Combination HRT/HT is estrogen combined with progestin. This type of HRT/HT can increase the risk of breast cancer.   - Exposure to radiation. Radiation therapy to the chest for the treatment of cancer can increase the risk of breast cancer, starting 10 years after treatment. Radiation therapy to treat cancer in one breast does not appear to increase the risk of cancer in the other breast.  - Obesity. Obesity increases the risk of breast cancer, especially in postmenopausal women who have not used hormone replacement therapy.   - Alcohol. Drinking alcohol increases the risk of breast cancer. The level of risk rises as the amount of alcohol consumed rises.  - Gaining weight after menopause, especially after natural menopause and/or after age 60.  - Race. White women are at greater risk than black women. However, black women diagnosed with breast cancer are more likely to die of the disease.  - Inherited gene changes. Women who have inherited certain changes in the genes named BRCA1 and BRCA2 have a higher risk of breast cancer, ovarian cancer and maybe colon cancer. The risk of breast cancer caused by inherited gene changes depends on the type of gene mutation, family history of cancer, and other factors. Men who have inherited certain changes in the BRCA2 gene have a higher risk of breast, prostate and pancreatic cancers, and lymphoma.    Five percent to 10 percent of all breast cancers are thought to be inherited.    Personal and family history. A personal history of breast cancer or breast cancer among one or more of your close relatives, such as a sister, mother, or daughter. Estrogen levels in the body. High estrogen levels over a long time may increase the risk of breast cancer. Estrogen levels are highest during the years a woman is menstruating. Never being pregnant or having your first child in your mid-30s or later. Early menstruation. Having your first menstrual period before age 12. Breast density. Women with very dense breasts have a higher risk of breast cancer than women with low or normal breast density. Combination hormone replacement therapy/Hormone therapy. Estrogen, progestin, or both may be given to replace the estrogen no longer made by the ovaries in postmenopausal women or women who have had their ovaries removed. This is called hormone replacement therapy. (HRT) or hormone therapy (HT). Combination HRT/HT is estrogen combined with progestin. This type of HRT/HT can increase the risk of breast cancer. Exposure to radiation. Radiation therapy to the chest for the treatment of cancer can increase the risk of breast cancer, starting 10 years after treatment. Radiation therapy to treat cancer in one breast does not appear to increase the risk of cancer in the other breast. Obesity. Obesity increases the risk of breast cancer, especially in postmenopausal women who have not used hormone replacement therapy. Alcohol. Drinking alcohol increases the risk of breast cancer. The level of risk rises as the amount of alcohol consumed rises. Gaining weight after menopause, especially after natural menopause and/or after age 60. Race. White women are at greater risk than black women. However, black women diagnosed with breast cancer are more likely to die of the disease. Inherited gene changes. Women who have inherited certain changes in the genes named BRCA1 and BRCA2 have a higher risk of breast cancer, ovarian cancer and maybe colon cancer. The risk of breast cancer caused by inherited gene changes depends on the type of gene mutation, family history of cancer, and other factors. Men who have inherited certain changes in the BRCA2 gene have a higher risk of breast, prostate and pancreatic cancers, and lymphoma.    Five percent to 10 percent of all breast cancers are thought to be inherited.   Get information about the BRCA1 and BRCA2 genetic mutations and testing for them. This chart shows what the approximate chances are of a woman getting invasive breast cancer in her lifetime.