Biological and Structural Factors Fuel Racial Disparities in Breast Cancer

In the US, there are known racial and ethnic disparities across health care and disease outcomes, and breast cancer is no exception. The causes of such disparities are multifaceted, Demetria Smith-Graziani, MD, MPH, a board-certified medical oncologist and assistant professor in the Department of Hematology and Medical Oncology at Winship Cancer Institute of Emory University School of Medicine, explained.

AJMC Q&A With Demetria Smith-Graziani, MD, MPH | Photo credit: Emory Winship Cancer Institute

In an interview with The American Journal of Managed Care^® (AJMC^®), Smith-Graziani spoke to the biological and societal drivers of breast cancer disparities in the US, which were the focus of her presentation at an AJMC Institute for Value-Based Medicine^® event held in Atlanta, GA, hosted jointly by AJMC and Emory Winship Cancer Institute.

This transcript was lightly edited for clarity.

What are some of the biological drivers of racial and ethnic disparities in breast cancer, and how can they be addressed?

Despite White women having a higher incidence of breast cancer in the United States, Black women have a 40% higher mortality.¹ Some of the biological things that we might think contribute to that are that Black women have a higher rate of triple-negative breast cancer, which we know is a more aggressive form of breast cancer. However, the most common breast cancer among Black women—as it is among all women—is still hormone receptor–positive breast cancer. We still see within that subtype of breast cancer that Black women have worse outcomes, and there are some data that suggest that Black women are more likely to have more aggressive forms of even the hormone receptor–positive breast cancer.²

We know there are these molecular subtypes of breast cancer that are associated with how aggressive breast cancer is and the likelihood of recurrence. For example, the luminal A molecular subtype of breast cancers are usually the most indolent types of cancer with the best prognosis, and we have seen data that show that Black women have a higher rate of these non–luminal A breast cancers, even when they have hormone receptor–positive disease.

Can you speak to the impact of structural racism on breast cancer disparities? How do structural barriers interact with the biological factors?

The structural racism that has existed in the United States for centuries affects the ability of Black women and other minoritized populations to get access to the care they need, and that can be because of geographic barriers—they might be in neighborhoods that have less access to hospitals and clinics, they might be in neighborhoods where there is less access to public transportation. It can also be that they are less likely to have insurance and less likely to have enough insurance to cover their medical needs. Black women can have lower incomes compared with White women because of the effects of structural racism.

But on top of that, even when we adjust for socioeconomic factors like education level, income, and insurance, even Black women who have the same socioeconomic status as a White counterpart tend to have worse outcomes when it comes to breast cancer,³ and some of that might be related to the effects of racism-related stress. There's some great data by our epidemiologist at Emory, Lauren McCullough [PhD]'s, group, showing that there is an association between the stress associated with the practice of redlining—in which the United States government basically worked across the country to segregate communities by denying mortgages to Black families in certain neighborhoods, creating certain pockets of neighborhood deprivation—and certain methylation changes that seem to be linked to inflammation and breast cancer outcomes, and as far as breast tumorigenesis, or the growth of breast cancer.⁴ So in addition to the actual socioeconomic effects, the stress associated with those things can be causing epigenetic changes that affect the type of breast cancer and the aggressiveness of the breast cancer.

Can you speak to the importance of racial and ethnic diversity in clinical trials and real-world analyses of breast cancer therapies?

Whenever we are applying data from a clinical trial to our patients, it is important that we feel the study population accurately represents our patient population—and historically, clinical trials have not had adequate representation of Black and other minoritized populations. At the bare minimum, we should be seeing a reflection of the diversity that exists in our country and within a particular disease group. For instance, to be in a city like Atlanta, where we have a very large Black population within the city itself—40-plus percent of our residents are Black—and yet, in clinical trials, the Black representation could be as low as 4%.

When we're thinking about all the things that we just discussed about potential differences in the way that cancer behaves among Black women, but also differences related to socioeconomic factors, not only are we limiting our ability to say that a treatment works just as well among our Black patients, but this also means that we are likely excluding Black patients from getting the best potential care they can. We know that people who received their cancer care at NCI [National Cancer Institute]–designated comprehensive cancer centers that have access to clinical trials have better outcomes overall, so just the ability to get to a major academic center and participate in a clinical trial increases the likelihood that you'll do better with your cancer. So we need to make sure that we are including Black women and other minoritized populations in clinical trials—not just so that we can confidently say that we know treatment works in our patient population, but also because it ensures that we are equitably giving people the opportunity to receive a new treatment that might be better than what exists as standard of care.

References

1. American Cancer Society. Breast Cancer Facts & Figures 2022-2024. Accessed August 19, 2024. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/breast-cancer-facts-and-figures/2022-2024-breast-cancer-fact-figures-acs.pdf

2. Keenan T, Moy B, Mroz EA, et al. Comparison of the genomic landscape between primary breast cancer in African American versus White women and the association of racial differences with tumor recurrence. J Clin Oncol. 2015;33(31):3621-3627. doi:10.1200/JCO.2015.62.2126

3. Zhao F, Copley B, Niu Q, et al. Racial disparities in survival outcomes among breast cancer patients by molecular subtypes. Breast Cancer Res Treat. 2021;185(3):841-849. doi:10.1007/s10549-020-05984-w

4. Maliniak ML, Moubadder L, Nash R, Lash TL, Kramer MR, McCullough LE. Census tracts are not neighborhoods: addressing spatial misalignment in studies examining the impact of historical redlining on present-day health outcomes. Epidemiology. 2023;34(6):817-826. doi:10.1097/EDE.0000000000001646