Rates of breast cancer in the U.S. vary by race and ethnicity. White women have the highest incidence (rate of new breast cancer cases) overall, while Asian American and Pacific Islander women have the lowest (see Figure 2.3 below) .
The main reason seems to be that different races and ethnicities simply have different prevalence rates of the established risk factors for breast cancer . Known risk factors that vary by race and ethnicity include [213-216]:
Learn more about these risk factors.
For example, compared to Hispanic/Latina women and African-American women, white women are more likely to put off childbirth and to have fewer children, each of which increases the risk of breast cancer [6,213,215,217].
Learn more about rates of breast cancer by race and ethnicity.
Although white women have higher rates of postmenopausal breast cancer compared to Africa-American women, African-American women have higher rates of premenopausal breast cancer . This may be due, in part, to differences in prevalence rates of some reproductive factors related to breast cancer risk. For example, compared to white women, African-American women tend to have an earlier age at first period, more lifetime periods and higher blood estrogen levels [218-220].
The biology of breast tumors also varies by race and ethnicity. Triple negative breast cancers are more common among African-American women than among women of other ethnicities [221-226]. Triple negative breast cancers are:
Triple negative tumors have a poorer prognosis compared to other subtypes of breast cancer. They tend to be higher grade and have a greater number of mutations in the p53 gene—factors also linked to a worse prognosis [216,227-229].
Although data are limited at this time, some lifestyle factors may play a role in the higher rate of triple negative breast cancer among African-American women. Some studies have found that compared to white women, African-American women tend to have lower rates of breastfeeding and tend to carry excess weight in the abdomen area, both of which may increase the chances of having triple negative tumors [217,223,230-231].
It may also be that certain reproductive and lifestyle factors protect more against estrogen receptor-positive (ER+) breast cancers than ER- breast cancers, including triple negative breast cancers. So, although African-American may be more likely than white women to have these protective factors, they may not lower the risk of triple negative breast cancers as much as they lower the risk of ER+ cancers. For example, African-American women are more likely than white women to [217,223,230-231]:
Although these factors lower the risk of breast cancer, this benefit may be limited to ER+ breast cancers [164,217,230-231]. There is even some evidence that these factors may increase the risk of triple negative breast cancers [164,217,230-231]. However, data are limited. These topics are under active study.
Learn more about the molecular subtypes of breast cancer, including triple negative breast cancer.
Learn more about rates of breast cancer by race and ethnicity and about differences in breast cancer rates in the U.S. and around the world.
Facts for Life: Racial & Ethnic Differences
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