What Causes Breast Cancer? . . We do not yet know exactly what causes breast cancer, but we do know that certain risk factors are linked to the disease. A risk factor is anything that increases a person's chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, such as smoking, can be controlled. Others, like a person's age or family history, can't be changed. But having a risk factor, or even several, doesn’t mean that a person will get the disease. . . Some women who have one or more risk factors never get breast cancer. And most women who do get breast cancer don’t have any risk factors. While all women are at risk for breast cancer, the factors listed below can increase a woman’s chances of having the disease. . . Risk Factors You Cannot Change . . Gender: simply being a woman is the main risk for breast cancer. While men can also get the disease, it is about 100 times more common in women than in men. . . Age: The chance of getting breast cancer goes up as a woman gets older. Nearly 8 out of 10 breast cancers are found in women age 50 or older. . . Genetic risk factors: About 5% to 10% of breast cancers are linked to changes (mutations) in certain genes. The most common gene changes are those of the BRCA1 and BRCA2 genes. Women with these gene changes have up to an 80% chance of getting breast cancer during their lifetimes. Other gene changes may raise breast cancer risk as well. . . Family history: Breast cancer risk is higher among women whose close blood relatives have this disease. The relatives can be from either the mother’s or father’s side of the family. Having a mother, sister, or daughter with breast cancer about doubles a woman’s risk. . . Personal history of breast cancer: A woman with cancer in one breast has a greater chance of getting a new cancer in the other breast or in another part of the same breast. This is different from the first cancer coming back (recurrence). . . Race: White women are slightly more likely to get breast cancer than are African-American women. But African American women are more likely to die of this cancer. Many experts now believe that the main reason for this is because they have faster growing tumors. Asian, Hispanic, and American Indian women have a lower risk of getting breast cancer. . . Abnormal breast biopsy: Certain types of abnormal biopsy results can be linked to a slightly higher risk of breast cancer. . . Earlier breast radiation: Women who have had radiation treatment to the chest area (as treatment for another cancer) earlier in life have a greatly increased risk of breast cancer. . . Menstrual periods: Women who began having periods early (before 12 years of age) or who went through the change of life (menopause) after the age of 55 have a slightly increased risk of breast cancer. . . Treatment with DES: In the past, some pregnant women were given the drug DES (diethylstilbestrol) because it was thought to lower their chances of losing the baby. Recent studies have shown that these women (and their daughters who were exposed to DES while in the uterus), have a slightly increased risk of getting breast cancer. For more information on DES see the American Cancer Society document "DES Exposure: Questions and Answers." . . Breast Cancer Risk and Lifestyles . . Not having children: Women who have had not had children, or who had their first child after age 30, have a slightly higher risk of breast cancer. Being pregnant more than once and at an early age reduces breast cancer risk. . . Birth control pills: It is still not clear what part birth control pills might play in breast cancer risk. Studies have found that women now using birth control pills have a slightly greater risk of breast cancer than women who have never used them. Women who stopped using the pill more than 10 years ago do not seem to have any increased risk. It’s a good idea to discuss the risks and benefits of bir