The relationship between race, ethnicity, and breast cancer is complex. Many studies show that women of different backgrounds have different rates of developing and surviving breast cancer, but the reasons for this aren't always clear. Lisa Ann Newman, MD, MPH, FACS, talked with Cancer.Net about race and breast cancer.

Q: What is known about race and breast cancer?

A: Differences in both the incidence (detection) and mortality (death) rates from breast cancer are well documented between populations defined by racial/ethnic background. These differences are also seen when comparing breast cancer rates in women from different continents. For example, women from Asia have notably lower breast cancer risks compared with American and European women.

The patterns in the United States with its diverse population reflect the patterns of breast cancer seen globally. For example, Asian American women have a lower risk of breast cancer than women with a European background do. The breast cancer rates of Latina/Hispanic American women tend to be between the rates observed in Asian American women and white women.

Breast cancer in black women has several poorly understood features:

• The overall lifetime risk of breast cancer is lower for black American women compared with white American women, but death rates are higher.
  
  
• Black women are diagnosed with breast cancer at a younger age.
  
  
• Women with breast cancer (at all ages) who are black have a higher rate of being diagnosed with more advanced stage/lymph node-positive disease. They are also more likely to have tumors that are more difficult to treat successfully, such as being estrogen receptor (ER)-negative and having a high-grade pathology (meaning that the cells from the tumor look more like cancer cells than healthy cells under a microscope).

Q: What factors are likely involved in these differences?

A: Several factors contribute to these differences. Communities of different racial/ethnic backgrounds (both worldwide and within the United States) frequently have differences in socioeconomic resources, reproductive patterns, and diet. These differences can affect breast cancer incidence, breast cancer mortality, or both.

Having access to health care is important in the outcome of breast cancer. Often, American women from traditional minority populations and women from underdeveloped countries have higher poverty rates and inconsistent medical care. These disadvantages cause delays in breast cancer diagnosis and treatment, ultimately resulting in lower survival rates.

Postmenopausal obesity, a high-fat diet, and delayed childbearing patterns are more common among American women compared with women in other parts of the world, and these factors are associated with a higher breast cancer risk. These factors also vary between population subsets within the United States, but as different communities gradually adopt American/westernized lifestyles, their breast cancer risks may change as well. For example, second- and third-generation Asian American women tend to have higher breast cancer risks compared to recent immigrants, with rates approaching those of white American women.

Q: What other factors still need to be identified and/or studied?

A: Specific dietary components and/or supplements may affect breast cancer risk, but the extent of these associations is not yet known. For example, eating a lot of soy products and phytoestrogens (frequently called "plant estrogens") has been considered a potential explanation for why Asian women have lower rates of breast cancer. However, in laboratory research studies, phytoestrogens have been shown to stimulate breast cancer growth.

The genetics of breast cancer that may be associated with racial/ethnic ancestry have also been identified in breast cancer disparities. For example, Ashkenazi (Eastern European) Jewish women have a higher risk of carrying particular mutations (abnormalities) in the BRCA breast cancer susceptibility genes, resulting in a very high risk for hereditary breast and/or ovarian cancer.

Recently, African ancestry has been linked with risk for particular breast cancer subtypes, such as the hormone-resistant and "triple-negative" (ER-negative, progesterone receptor [PR]-negative, and HER2-negative) tumors. An increased frequency of these patterns has been observed in African American women in the United States and sub-Saharan western African women (who have shared ancestry because of the slave trade locations from the colonial era). Interestingly, male breast cancer is also more common among African as well as African American men. Since Africa is the site for the founder populations of all humankind, genetic markers of cancer risk that are present in contemporary African populations may also be found in European and white American populations. The frequency of these markers however, might be different because of the migration patterns and intermixing of different populations over several centuries.

Q: What research is being done to address these factors?

A: Many researchers are studying the role of various nutrients for either the prevention or cause of the formation and development of breast cancer. These studies are underway in the laboratory and in clinical trials (research studies). It is extremely important that we have women of all racial/ethnic backgrounds participating in these clinical trials, so that we can better understand how these nutrients prevent or lead to breast cancer.

Also, international collaborations are now underway to study breast cancer in women from the Americas, Africa, Asia, and throughout the world. As these partnerships move forward, and as biomedical technology continues to advance, we will be able to disentangle the effects of socioeconomic status, diet, lifestyle, and genetics on breast cancer disparities.

Inequities in health care access and delivery must be corrected. Breast cancer screening, detection, and treatment should be universally available on a cost-efficient basis. Partnerships between public policy experts, advocates, and the cancer community are essential in these efforts.

Q: What does this mean for people with breast cancer?

The goal of these multidisciplinary research efforts is to identify specific factors of breast cancer risk that can help researchers find specific ways to treat and prevent breast cancer. For example, we may be able to identify nutritional supplements or diets that can lower breast cancer risk and/or improve the results of treatment. From genetic studies of racial/ethnic ancestry, researchers may find markers identifying those at risk for hormone-resistant breast cancer, and these markers might in turn become valuable for prevention and treatment efforts.

Dr. Newman is the Director, Breast Care Center, and Associate Professor of Surgery at the University of Michigan. She is a member of the Cancer.Net Editorial Board and the ASCO Health Disparities Task Force

More Information

Cancer.Net Guide to Breast Cancer

The Genetics of Breast Cancer

Additional Resources

National Cancer Institute: Cancer Health Disparities

Susan G. Komen for the Cure: Race and Ethnicity

Last Updated: September 06, 2007