Every woman wants to know what her risk of getting breast cancer is and what she can do about it.
The term "risk factor" refers to identifiable factors that make some people more susceptible than others to a particular disease. In breast cancer, we have come up with some risk factors. But so far, there is nothing comparable to the connections found between smoking and lung cancer. In fact, 70 percent of breast cancer patients have none of the known risk factors.
Important Points - Risk factors don't necessarily increase in a simple arithmetic fashion: If one risk factor gives you a 20 percent risk of getting breast cancer, and another gives you a 10 percent chance, it doesn't always mean that now you're up to 30 percent. The interaction of risk factors is a tricky and complicated process.
- The older you are, the higher your chances are of getting breast cancer. Most breast cancer occurs in women over 50—about 80 percent of cases. So whenever you look at risk factors, you need to correct for age. Other risk factors—family history, hormonal factors, etc.—will most likely cause breast cancer only in combination with rising age.
- There is an impression that more young women are now getting breast cancer. That's partially true. The percentage of young women getting breast cancer hasn't changed. But the number of younger women in the country has increased. If you take 10 percent of 40, you get 4; if you take 10 percent of 400, you get 40. There are more 40-something women with breast cancer because there are more 40-something women around.
- Risk factors vary by race/ethnicity.
| Probability of a Woman Developing Breast Cancer by Age 75 by Race/Ethnicity* | | | % | No. | | White | 8.2 | 1 in 12 | | African-American | 7.0 | 1 in 14 | | New-Mexican Hispanic | 4.8 | 1 in 21 | | New-Mexican American Indian | 2.5 | 1 in 40 | | Japanese-American | 5.4 | 1 in 19 | | Chinese-American | 6.1 | 1 in 16 | Note: Table calculates risk to age 75 (1 in 12) rather than the familiar 1 in 8 calculated to age 85.
*J. W. Berg, "Clinical Implications of Risk Factors for Breast Cancer," Cancer 53 (1984): 589. Reprinted with permission. |
Genetic Risk Factors
We divide breast cancer occurrences into three groupings. The first, and most common, is sporadic—that's the women with breast cancer who have no known family history of the disease. The second is genetic—there's one dominant cancer gene, and it's passed on to the succeeding generations. The third is polygenic, and it occurs when there is a family history of breast cancer that isn't directly passed on through each generation in one dominant gene—some members of the family will get it and others won't. Women in this category are at greater risk for cancer than the general public, though less so than women with hereditary cancer.
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