Over the course of a lifetime, one in eight women will be diagnosed with breast cancer.
Risk factors you cannot change include:
Age and gender — Your risk of developing breast cancer increases as you get older. The majority of advanced breast cancer cases are found in women over age 50. Women are 100 times more likely to get breast cancer than men.
Family history of breast cancer — You may also have a higher risk for breast cancer if you have a close relative who has had breast, uterine, ovarian, or colon cancer. About 20 to 30 percent of women with breast cancer have a family history of the disease.
Genes — Some people have genes that make them more prone to developing breast cancer. The most common gene defects are found in the BRCA1 and BRCA2 genes. These genes normally produce proteins that protect you from cancer. But if a parent passes you a defective gene, you have an increased risk for breast cancer. Women with one of these defects have up to an 80 percent chance of getting breast cancer sometime during their life.
Menstrual cycle — Women who get their periods early (before age 12) or went through menopause late (after age 55) have an increased risk for breast cancer.
Other risk factors include:
Alcohol use — Drinking more than one to two glasses of alcohol a day may increase your risk for breast cancer.
Childbirth — Women who have never had children or who had them only after age 30 have an increased risk for breast cancer. Being pregnant more than once or becoming pregnant at an early age reduces your risk of breast cancer.
DES — Women who took diethylstilbestrol (DES) to prevent miscarriage may have an increased risk of breast cancer after age 40. This drug was given to the women in the 1940s - 1960s.
Hormone replacement therapy (HRT) — You have a higher risk for breast cancer if you have received hormone replacement therapy for several years or more. Many women take HRT to reduce the symptoms of menopause.
Obesity — Obesity has been linked to breast cancer, although this link is controversial. The theory is that obese women produce more estrogen, which can fuel the development of breast cancer.
Radiation — If you received radiation therapy as a child or young adult to treat cancer of the chest area, you have a significantly higher risk for developing breast cancer. The younger you started such radiation and the higher the dose, the higher your risk -- especially if the radiation was given when a female was developing breasts.
Breast implants, using antiperspirants, and wearing underwire bras do not raise your risk for breast cancer. There is no evidence of a direct link between breast cancer and pesticides.