Posted: October 28, 2016
October is Breast Cancer Awareness Month, and on this occasion, I’d like to highlight some important facts about breast cancer and African-American women: First, African-American women who have breast cancer are more likely to die from the disease than women of any other racial or ethnic group. Second, they are more likely to have advanced disease. And third, they more likely to have triple-negative breast cancer, which does not respond to hormonal therapy.
Why is this? We don’t know for sure. And that’s where the National Cancer Institute’s (NCI’s) Breast Cancer Genetic Study in African-Ancestry Populations comes in. This is the largest study ever to look at how genetics might contribute to the higher death rate for African-American women.
The study involves 40,000 African-American women—half of whom have breast cancer and half of whom do not. The study will also compare white women and African-American women with breast cancer. By comparing these groups, we expect to better understand how genes can raise or lower the risk of breast cancer. This information will be useful for all women diagnosed with this disease.
I sat down with Dr. Damali Martin, the Program Director of the NCI’s Genomic Epidemiology Branch, to talk about the study.
JC: This is an ambitious project. How did it come about?
DM: This study builds on previous studies done by the NCI-supported African-American Breast Cancer Consortium, the African-American Breast Cancer Epidemiology and Risk (AMBER) Consortium, and the NCI Cohort Consortium. As you mentioned, researchers will compare the genes of 20,000 African-American women with breast cancer to the genes of 20,000 African-American women without breast cancer. This comparison will help identify genetic variables that are associated with both estrogen-receptor-negative and estrogen-receptor-positive breast cancer in this population.
JC: Why is it important to study breast cancer in African-American women?
DM: First, I should say that breast cancer survival rates have improved in the United States. But African-American women still experience 42 percent higher mortality compared to their white counterparts and are more likely to be diagnosed with late-stage breast cancer.[i]
African-American women are more often diagnosed with triple-negative or basal-like breast cancers, which are the most aggressive subtype. For example, approximately 22 percent of breast cancers in African-American women are triple negative compared to 10–12 percent in other ethnic or racial groups.[ii] These disparities are even higher among premenopausal African-American women with breast cancer.
It’s important to support research that investigates the causes of these cancer disparities, which include social factors (access to health care, neighborhood environment, socioeconomic status) and genetic and other biological factors. Understanding the social and biological causes that lead to disparities in cancer among underserved populations is a top priority at the NCI. The Institute is committed to supporting outstanding research that will increase our knowledge of factors that contribute to cancer disparities and methods that can be used to reduce them.
JC: You mentioned that African-American women tend to get more aggressive types of breast cancer. Do we know why?
DM: In general, African-American women with breast cancer are diagnosed with late-stage disease more often than women from other racial and ethnic groups. The reasons for this may be related to unequal access to mammography or other high-quality health care, low socioeconomic status, lack of education, and other factors that may delay diagnosis.
However, it is important to note that differences in breast cancer outcomes in African-American women may in part be due to differences in the subtypes of cancer, which may have different underlying causes—genetic and environmental factors or, more likely, both. Indeed, some studies suggest that African-American women are more likely to be diagnosed with triple-negative breast cancer as a result of African ancestry that may reflect specific genetic factors.[iii]
Research has also suggested that risk factors for triple-negative subtypes may include behavioral risk factors, such as decreased rates of breastfeeding or other environmental influences. All of these studies indicate that a variety of factors may work together to cause aggressive breast cancer in African-American women. Thus, research is needed to better understand how biological and non-biological risk factors and their subsequent interactions contribute to breast cancer disparities experienced by African-American women.
JC: ORWH and NIH are putting more emphasis on how genetic and other biological variables influence health and disease. It sounds like this study takes a similar approach.
DM: Yes. This research will enable us to learn more about the genetic and other biological factors that contribute to the risk of breast cancer in African-American women. It will help us identify how these factors compare to similar factors affecting white women. Researchers for this study will be connecting data on biological factors to other data, such as data on one’s neighborhood or environment, to understand how all of these factors work together to increase the risk of breast cancer among African-American women. As we move toward personalized medicine or implement other large scientific initiatives, such as the President’s Precision Medicine Initiative, it is important to ensure that every person, regardless of his or her background, has the opportunity to benefit from these research advances.
JC: Women now comprise more than half of all NIH-funded study participants. Why is it important for African-American women, in particular, to participate in studies such as this one?
DM: The results from one study group don’t necessarily apply to another study group. It’s important for African-American women to participate in research studies to help us understand why they, in particular, tend to be diagnosed more frequently with late-stage breast cancer or more aggressive forms of breast cancer than women of other racial and ethnic groups, and also why they have a higher mortality rate than white women.
JC: Historically, it’s been difficult to pursue studies such as this one in minority populations because the number of minorities who participate in clinical or epidemiologic studies is quite low.
DM: While researchers from earlier studies were able to gain some insights regarding the genetic risk of breast cancer in African-American women, their successes were limited due to the smaller number of women in each study. This larger study of 20,000 African-American breast cancer patients and an additional 20,000 African-American women without breast cancer was made possible through the collaborative effort of the researchers who led the previous studies and through the participation of those women in those studies.
JC: Any knowledge we gain from this study could have potential benefits for everyone. The more we know, the better equipped we are to provide optimal treatment options. What are the potential outcomes of this study?
DM: Once this five-year study is completed, we will have a greater understanding of how genetic variants influence the risk of breast cancer in African-American women. Researchers will have a better understanding of the underlying disease biology, which we hope can be used to identify women who are at higher risk for breast cancer and help prevent it. Although we are focusing on African-American women, we expect to learn much that will be useful for all women with breast cancer.
This research investment, in combination with previous and other ongoing investments, will continue to accelerate the pace of breast cancer research and will eventually help us understand risk factors that contribute to breast cancer-related disparities.
This study demonstrates the power and importance of data sharing and would not be possible without the strong collaboration and sharing of data and biospecimens—one of the priorities under Vice President Joseph Biden’s Cancer Moonshot Initiative. Additional studies are needed and are ongoing to advance treatment strategies for women who develop breast cancer. The participation of all women, but especially African-American women, in these studies is important to ensure any new approaches developed take into account their specific genetic, environmental, and lifestyle factors—the focus of NIH’s Precision Medicine Initiative.
JC: Thank you so much for taking the time to talk about this research, Dr. Martin. I believe this study could help improve the health of every woman. Shall we agree to meet again in a few years to discuss progress?
DM: Yes, I’d really like that! We have a lot of hard work to do between now and then, but I am excited and very hopeful about this project.
[i] DeSantis, C. E., et al. (2016). Breast cancer statistics, 2015: Convergence of incidence rates between black and white women. CA: A Cancer Journal for Clinicians, 66, 31-42.
[ii] DeSantis, C. E., et al. (2016). Breast cancer statistics, 2015: Convergence of incidence rates between black and white women. CA: A Cancer Journal for Clinicians, 66, 31-42.
[iii] Brewster A. M., et al. (2014) Epidemiology, biology, and treatment of triple-negative breast cancer in women of African ancestry. Lancet Oncol, 15, e625-e634.