Scientists at Duke are studying the causes of breast cancer to learn more about risk factors and ways of preventing this disease.
At present, the exact causes of breast cancer are not known. However, studies show that the risk of breast cancer increases as a woman gets older.
This disease is very uncommon in women under age 35. Most breast cancers occur in women over 50, and the risk is especially high for women over 60. Also, breast cancer occurs more often in white women than African-American or Asian women.
Risk Factors
Certain conditions or exposures can increase your risk of getting breast cancer. Even if you don’t have any of the common risk factors, you may still be at some risk of having cancer in the future.
Risk factors include:
- Gender, age, and race. Women get the majority of breast cancers; less than 1 percent of all breast cancers are in men. The risk for breast cancer increases with age. Whites are more likely to develop it than African-American women, though African-Americans tend to develop breast cancer types that are more aggressive.
- Past history of breast cancer. Women who have had cancer in one breast have an increased risk of developing a second cancer in the same breast or the other breast.
- Lifestyle factors. Drinking two or more alcoholic drinks a day increases risk, as does lack of exercise or physical activity, being overweight, or being obese.
- Family history. A woman's risk for developing breast cancer increases if her mother, sister, or daughter had breast cancer, especially at a young age.
- Certain breast changes. Having a diagnosis of atypical hyperplasia or lobular carcinoma in situ (an irregular pattern of cell growth) may increase a woman's risk for developing cancer.
- Genetic alterations. About 5 percent of breast cancers are linked to changes (mutations) in certain genes. Studies show that some breast cancer is linked to changes of the BRCA1 and BRCA2 genes. If a woman has inherited a mutated gene from either parent, she is more likely to develop breast cancer. About 50 to 60 percent of women with these inherited changes will develop breast cancer by the age of 70. Other genetic mutations that bring less of a risk than BRCA1 and BRCA2 include ATM, p53, p53, CHEK2, PTEN, and CDH1a.
- Estrogen. Evidence suggests that the longer a woman is exposed to estrogen (estrogen made by the body, taken as a drug, or delivered by a patch), the more likely she is to develop breast cancer. For example, the risk is somewhat increased among women who began menstruation at an early age (before age 12), experienced menopause late (after age 55), never had children, or took hormone replacement therapy for long periods of time. Also, women who have their first child late (after about age 30) have a greater chance of developing breast cancer than women who have a child at a younger age.
- Breast density. Breasts that have a high proportion of lobular and ductal tissue appear dense on mammograms. Breast cancers nearly always develop in lobular or ductal tissue (not fatty tissue).
- Radiation therapy. Women whose breasts were exposed to radiation during radiation therapy before age 30, especially those who were treated with radiation for Hodgkin's disease, are at an increased risk for developing breast cancer. Studies show that if treatment was received during the period of breast development, the woman has a higher risk for developing breast cancer later in life.
Learn more about breast cancer:
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