What’s Driving Higher Breast Cancer Deaths in Black Women?
More women today are surviving breast cancer if it’s caught early, largely because of better screening and more effective and targeted treatments.
However, not everyone has benefited equitably from this progress. Critical gaps in breast cancer outcomes and survival remain for women in racial and ethnic minority groups.
Black women for instance, have a 41% higher death rate from breast cancer compared with White patients. They also have a greater incidence of aggressive disease like triple-negative breast cancer. Native American and Hispanic women, meanwhile, are more likely to be diagnosed with breast cancer at an earlier age than White women and experience more aggressive breast cancers.
In 2023, Farhad Islami, MD, PhD, and his team published an updated analysis of racial/ethnic and socioeconomic disparities in cancer trends based on data from 2014 to 2020. The analysis found that Black women in particular, were the least likely to have an early-stage diagnosis of breast cancer. Localized‐stage breast cancer was diagnosed in 57% of Black women versus 68% of White women.
“Despite substantial progress in cancer prevention, early detection, and treatments, the burden of cancer remains greater among populations that have been historically marginalized, including people of color, people with lower socioeconomic status, and people living in nonmetropolitan areas,” said Dr. Islami, who is senior scientific director of cancer disparity research in the Surveillance & Health Equity Science Department at the American Cancer Society.
The reasons behind outcomes disparities in breast cancer are complex, making solutions challenging, say experts researching racial differences in cancer outcomes.
While social determinants of health (SDH) seem to be drivers of higher breast cancer mortality in Black women, biological differences between Black and White women are also linked to poorer outcomes in Black women with breast cancer, new studies suggest. Among the findings of this research is that breast cancer tests may be contributing to the disparities and misguiding care for some patients of color.
SDH and Screening Rates Differences by Race
A range of factors contribute to racial and ethnic disparities in breast cancer outcomes, said Pamela Ganschow, MD, an associate professor in the Department of Internal Medicine at the University of Illinois Cancer Center in Chicago and part of the university’s Cancer Prevention and Control research program. These include socioeconomic status, access to timely and high-quality care across the cancer control continuum, cultural beliefs, differences in genetic makeup and tumor biology, as well as system biases, such as implicit biases and systemic racism, Dr. Ganschow said.
Dr. Islami adds that gaps in access to cancer prevention, early detection, and treatment are largely rooted in fundamental inequities in social determinants of health (SDH), such as whether a patient has safe housing, transportation, education, job opportunities, income, access to nutritious foods, and language and literacy skills, among others.
Dr. Islami’s analysis, for example, shows that people of color are generally more likely to have lower educational attainment and to experience poverty, food insecurity, and housing insecurity compared with White people. Among people aged 18-64 years, the age-adjusted proportion of individuals with no health insurance in 2021 was also higher among Black (13.7%), American Indian/Alaskan Native (18.7%), and Hispanic (28.7%) patients than among White (7.8%) or Asian (5.9%) people, according to the report.
Competing needs can also get in the way of prioritizing cancer screenings, especially for patients in lower socio-economic populations, Dr. Ganschow said.
“You’ve got people who are working a job or three jobs, just to make ends meet for their family and can’t necessarily take time off to get that done,” she said. “Nor is it prioritized in their head because they’ve got to put a meal on the table.”
But the racial disparities between Black and White women, at least, are not clearly explained by differences between the screening rates.
Of patients who received mammograms 76% were White and 79% were Black, according to another recent study coauthored by Dr. Islami. While Black women appear to have the highest breast cancer screening rates, some data suggest such rates are being overreported.
Lower screening rates were seen in American Indian/Alaska Native (59%), Asian (67%), and Hispanic women (74%).
Biological Differences, Bad Testing Recommendations May Contribute to Poor Outcomes
Differences in biology may be one overlooked internal driver of lower breast cancer survival in Black women.
Researchers at Sanford Burnham Prebys in La Jolla, California, recently analyzed the breast cells of White and Black women, finding significant molecular differences that may be contributing to higher breast cancer mortality rates in Black women.
Investigators analyzed both healthy tissue and tumor tissue from 185 Black women and compared the samples to that of White women. They discovered differences among Black and White women in the way their DNA repair genes are expressed, both in healthy breast tissue and in tumors positive for estrogen receptor breast cancer. Molecular differences were also present in the cellular signals that control how fast cells, including cancer cells, grow.
DNA repair is part of normal cellular function and helps cells recover from damage that can occur during DNA replication or in response to external factors, such as stress.
“One of the first lines of defense, to prevent the cell from becoming a tumor are DNA damage repair pathways,” said Svasti Haricharan, PhD, a coauthor of the study and an assistant professor at Sanford Burnham Prebys. “We know there are many different DNA damage repair pathways that respond to different types of DNA damage. What we didn’t know was that, even in our normal cells, based on your race and ethnicity, you have different levels of DNA repair proteins.”
The study found that many of the proteins associated with endocrine resistance and poor outcomes in breast cancer patients are differently regulated in Black women compared with White woman. These differences contribute to resistance to standard endocrine therapy, Dr. Haricharan said.
“Because we never studied the biology in Black woman, it was just assumed that across all demographics, it must be the same,” she said. “We are not even accounting for the possibility there are likely intrinsic differences for how you will respond to an endocrine treatment.”
Testing and treatment may also be playing a role in worse breast cancer outcomes for Black women.
In an analysis of 73,363 women with early-stage, estrogen receptor–positive breast cancer, investigators found that a common test used to decide the treatment course for patients may be leading to bad recommendations for Black women.
The test, known as the 21-gene breast recurrence score, is the most commonly ordered biomarker test used to guide doctor’s recommendations for patients with estrogen receptor–positive breast cancer, the most common form of cancer in Black women, representing about 70%-80% of cases.
The test helps physicians identify which patients are good candidates for chemo, but the test may underestimate the benefit of chemo for Black women. It ranks some Black women as unlikely to benefit from chemo, when they actually would have benefited, according to the January 2024 study, published in the Journal of the National Comprehensive Cancer Network.
The test gives a score of zero to 100, explains Kent Hoskins, MD, oncology service line medical director at the University of Illinois (UI) Health and director of the Familial Breast Cancer Clinic at UI Health, both in Chicago. The higher the score, the higher the risk and the greater the benefit of chemotherapy. A patient is either above the cut-off score and receives chemo or is below the cut-off score and does not. In the analysis, investigators found that Black women start improving with chemo at a lower score than White women do.
Dr. Hoskins said the results raise questions about whether the biomarker test should be modified to be more applicable to Black women, whether other tests should be used, or if physicians should judge cut-off scores differently, depending on race.
How Neighborhood Impacts Breast Cancer, Death Rates
Living in a disadvantaged neighborhood also lowers breast cancer survival, according to new research. A disadvantaged neighborhood is generally defined as a location associated with higher concentrations of poverty, higher rates of unemployment, and less access to health care, quality housing, food, and community resources, according to the Centers for Disease Control and Prevention.
Authors of a study published in JAMA Network Open on April 18 identified 350,824 patients with breast cancer. Of these, 41,519 (11.8%) were Hispanic, 39,631 (11.3%) were non-Hispanic Black, and 234,698 (66.9%) were non-Hispanic White. Investigators divided the patients into five groups representing the lowest to highest neighborhood socioeconomic indices using the Yost Index. (The Yost index is used by the National Cancer Institute for cancer surveillance and is based on variables such as household income, home value, median rent, percentage below 150% of the poverty line, education, and unemployment.)
Of the Black and Hispanic patients in the study, the highest proportions of both demographics lived in the most disadvantaged neighborhoods. (16,141 Black patients [30.9%]) and 10,168 Hispanic patients [19.5%]). Although 45% of White patients also fell into that same category, the highest proportion of White patients in the study lived in the most advantaged neighborhoods (66,529 patients [76.2%]).
Findings showed patients in the most disadvantaged neighborhoods had the highest proportion of triple-negative breast cancer. Patients in this group also had the lowest proportion of patients who completed surgery and radiation, and the highest proportion of patients who received chemotherapy, compared with all other neighborhood groups. The most advantaged neighborhoods group had higher proportions of localized-stage cancer, a higher proportion of patients who underwent surgery and radiation, and the lowest proportion of patients receiving chemotherapy treatment.
Patients in the most disadvantaged neighborhoods also had the highest risk of mortality (hazard ratio [HR], 1.53; 95% CI, 1.48-1.59; P less than .001) compared with patients living in the most advantaged neighborhoods. Non-Hispanic Black patients in particular, had the highest risk of mortality, compared with non-Hispanic White patients (HR, 1.16; 95% CI, 1.13-1.20; P less than .001).
Authors wrote that the findings suggest neighborhood disadvantage is independently associated with shorter survival in patients with breast cancer, even after controlling for individual-level factors, tumor characteristics, and treatment.
“To address these residual disparities associated with neighborhood disadvantage, research must focus on which components of the built environment influence outcomes,” the authors said.
Another recent study also found correlations among where breast cancer patients lived and how they fared with the disease.
Jasmine M. Miller-Kleinhenz, PhD, an assistant professor at University of Mississippi Medical Center in Jackson, studied how historical redlining impacts breast cancer development and outcomes in her research published in JAMA Network Open, earlier this year. Redlining refers to the practice of denying people access to credit because of where they live. Historically, mortgage lenders widely redlined neighborhoods with predominantly Black residents. The 1968 Fair Housing Act outlawed racially motivated redlining, but consequences from historical redlining still exist.
Dr. Miller-Kleinhenz and her colleagues analyzed a cohort of 1764 women diagnosed with breast cancer between January 2010 and December 2017, who were followed up through December 2019. Investigators accessed the cohort based on three exposures: historic redlining (HRL), contemporary mortgage discrimination (CMD), and persistent mortgage discrimination (PMD). Contemporary mortgage discrimination refers to current-day discriminatory mortgage practices and persistent mortgage discrimination refers to neighborhoods that have experienced both HRL and CMD.
Findings showed that Black women living in historical redlined areas had increased odds of being diagnosed with aggressive forms of breast cancer, while White women in redlined areas had increased odds of late-stage diagnosis.
White women exposed to persistent mortgage discrimination were twice as likely to die of breast cancer, compared with their White counterparts living in areas without historical redlining or contemporary mortgage discrimination, the study found.
That is not to say that Black women did not have an increased risk of breast cancer mortality, Dr. Miller-Kleinhenz explained. Black women had a more than threefold elevated risk of breast cancer mortality compared with White women no matter where they lived, according to the findings.
“These results were surprising because it is showing that while neighborhood conditions might be a major driver of breast cancer mortality in White women, there are factors beyond the neighborhood that are additional drivers that are contributing to poor outcomes in Black women,” she said.
Hope for Improved Outcomes, Higher Survival Rates
Investigators hope the findings of all of this new research lead to better, more targeted treatments and, in turn, improved outcomes.
Dr. Haricharan is optimistic about the improvement of breast cancer outcomes as more is learned about the biology of Black patients and other non-White patients.
There is a growing effort to include more data from minoritized populations in breast cancer research studies, Dr. Haricharan said, and she foresees associated changes to clinical protocols in the future. Her own team is working on creating larger data sets that are more representative of non-White patients to further analyze the differences found in their prior study.
“I think there’s this understanding that, until we have data sets that are more representative, we really are catering to [only one] population in terms of our diagnostic and therapeutic technological advances,” she said.
The American Cancer Society meanwhile, is launching a new initiative in May that aims to collect more health data from Black women to ultimately develop more effective cancer interventions. VOICES of Black Women will focus on collecting and studying health data from Black women through online surveys. The society’s goal is to enroll at least 100,000 Black women in the United States between ages 25 and 55.
Dr. Miller-Kleinhenz called the initiative “an important step to starting to research and answer some of these lingering questions about why there continue to be breast cancer disparities.”
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
