What Makes a Woman Likely to Get Breast Cancer?
There's no way yet to predict who is most likely to get breast cancer. Although a few men get the disease, the overwhelming majority of people with breast cancer are women. Research shows some women have a higher chance of getting the disease than others. Before age 45, African American women have the highest chance of getting breast cancer, compared to women from other ethnic groups. After age 45, white women are most likely to get the disease.
Here's a summary of characteristics that can lower or raise a woman's chances of getting breast cancer. Each characteristic by itself has only a small effect on risk.
These Characteristics Raise a Woman's
These Characteristics Lower a Woman's
|Older Age||Younger Age|
|Jewish||No corresponding factor|
|Higher income and more education||Lower income and less education|
|Immigrated from a low-income nation to a highincome nation||No corresponding factor|
|Never had a baby||No corresponding factor|
|Had first baby after age 30||Had first baby after age 20|
|Began menstruating before age 12||Began menstruating after age 12|
|Reached menopause after age 55||Reached menopause before age 55|
|Taking or recently took estrogen replacement therapy (especially for many years with high-dose combined estrogen and progestin)||No corresponding factor|
|Taking birth control pills or took them less than 10 years ago||No corresponding factor|
|After menopause, higher weight relative to height||Before menopause, higher weight relative to height|
|Drinking two or more alcoholic drinks per day||Regular exercise as an adult|
|No corresponding factor||Exercise as a teenager reduces the chance of getting breast cancer before menopause|
|Exposure to radiation (at higher levels than from mammograms)||No corresponding factor|
|Inheriting breast cancer susceptibility genes||No corresponding factor|
|A sister, mother, or both who had breast cancer||No corresponding factor|
|Already had breast cancer||No corresponding factor|
|Had benign breast disease, especially atypical hyperplasia||No corresponding factor|
|On a mammogram, breasts look very dense||No corresponding factor|
In about half of all breast cancer cases, none of the characteristics listed on the previous page make any difference. Inherited genes, for example, play a role in only 5 to 10 percent of breast cancer cases. In addition, most of the characteristics listed above are probably not direct causes. We don't know why they affect a woman's risk for breast cancer. What makes a particular woman get breast cancer is still a puzzle that can only be solved with more research.
How This Research Was Done
Researchers summarized results from many scientific studies published in respected journals over the past decade. The studies summarized here were for the most part based on samples of women from the U.S. population, and they did not necessarily include women from California. Information in this section comes from Chapter 2 of Breast Cancer in California, 2003, “Risk Factors for Female Breast Cancer,” by Rosemary D. Cress, Dr.P.H.