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Experts know that racial disparities in healthcare play a role in breast cancer mortality, but could molecular factors also contribute? Santi Nuñez/Stocksy
  • Researchers from Sanford Burnham Prebys led a new study that explored why Black women with breast cancer have a higher mortality rate than white women with breast cancer.
  • The researchers learned that there is a molecular difference between the processes for repairing damaged DNA within the cells.
  • The results of the study indicate that doctors may need to adjust treatment plans for Black women with breast cancer to improve their chances of surviving.

Less positive outcomes in Black women with breast cancer are due, at least in part, to racial disparities in healthcare.

The authors of one paper write, “Despite medical improvements in early detection, diagnosis, and screening, many Black women are less likely to obtain adequate treatment compared with white women.”

A new study, which appears in Therapeutic Advances in Medical Oncology, indicates that biological factors may add to this disparity.

The study examined genetic differences between Black women and white women and found that there is a difference in the cellular response to damaged DNA.

According to the Centers for Disease Control and Prevention (CDC), in the United States, about 255,000 women develop breast cancer each year, and approximately 42,000 women die. Overall, breast cancer is the second leading cause of cancer death among women.

The demographic data for 2018 indicated that the rate of breast cancer occurrence between Black women and white women was similar.

Among Black women, the rate of new breast cancer cases was 121.2 per 100,000 women. In comparison, among white women, the rate was 127.5 per 100,000.

Although there was only a 5% difference in the breast cancer case rate between Black women and white women, the difference in mortality rate was much greater.

According to the 2018 data, white women had a breast cancer mortality rate of 19.2 per 100,000 cases, and the mortality rate for Black women was 26.8 per 100,000 cases. This equates to an approximately 40% higher rate in Black women than in white women.

Dr. Lola Fayanju speaks about breast cancer in a podcast with, in which she notes the difference in mortality rate. Dr. Fayanju is the surgical director at Rena Rowan Breast Center in Philadelphia.

“In the United States, white women are actually the most likely to be diagnosed with breast cancer of any racial or ethnic group,” Dr. Fayanju says. “But there are significant disparities in terms of who is most likely to die from breast cancer, which is, for the most part, a highly curable disease.”

“For early stage breast cancer, rates of survival are often greater than 90%, but among Women of Color, particularly African American women, we see much worse mortality rates, and that’s in part related to the fact that we have people presenting with later stage disease,” Dr. Fayanju explains.

Some studies indicate that socioeconomic status is an important cause of the increased mortality rate. It contributes to Black women not having the same access to healthcare, which creates issues with preventive care, cancer detection, and treatment.

Although the researchers behind the new study acknowledge that this disparity factors into higher mortality rates among Black women, their research suggests that a molecular difference also contributes.

According to Dr. Svasti Haricharan, lead author of the study, “society has internalized the narrative that lifestyle factors are to blame for racial differences in health outcomes, so most scientists don’t look at molecule-level differences between people.”

Dr. Haricharan is an assistant professor in the Aging, Cancer, and Immuno-oncology Program at Sanford Burnham Prebys Medical Discovery Institute in La Jolla, CA.

The team compared both estrogen receptor-positive (ER-positive) cancerous tissue and normal breast tissue from Black and white women. They found that in both normal and cancerous tissue, eight DNA damage response and repair (DDR) genes in Black women functioned differently.

Some of the dysregulated DDR genes inhibited the repair response.

“What we’re seeing here is a tangible molecular difference in how these cells repair damaged DNA — a critical factor in the development of cancer — which affects how cells grow and reproduce in tumors,” says Dr. Haricharan.

Based on the findings of the study, doctors may need to adjust treatment plans for Black women with breast cancer.

“This is something we can act upon immediately because helping these women is less about finding a new drug and more about changing the timing for treatments we already have available,” says Dr. Haricharan.

The researchers mentioned that doctors use cyclin-dependent kinase inhibitors in the later stages of treatment for ER-positive breast cancer. However, they may be able to introduce this earlier in Black women with breast cancer to give them a better outlook.

“This is so important because if the normal tissue is different at the molecular level based on race or ethnicity, then everything we understand about how each of us responds to cancer treatment is going to be different, as well.”

– Dr. Haricharan

Dr. Haricharan spoke with Medical News Today about the study and discussed the team’s plans for the future. She outlined some next steps:

“Creating a large molecular database that represents breast cancer in Black women — which is currently lacking — in order to fully understand the molecular drivers that are unique to breast cancer cells in Black women.”

“Black women are severely underrepresented in virtually all datasets of patient tumors, so a lot of previous results about breast cancer only accurately reflect what’s happening to white women,” said Dr. Haricharan. “We hope our research will highlight the need to study cancer in different racial and ethnic groups more closely and improve outcomes for historically marginalized patients.”

She would also like to test “the molecular relationships we observe between the DNA repair signature occurring in ER-positive breast cancer samples in Black women and response to cell cycle inhibitors […] using experimental model systems.”

Cell cycle inhibitors include palbociclib (Ibrance), which, as Dr. Haricharan explained, “is already [approved by the Food and Drug Administration {FDA}] for late stage ER-positive breast cancer but may be beneficial to provide to Black women with ER-positive breast cancer early on in their disease timeline.”

Another important step, which Dr. Haricharan recognized as “the largest hurdle to doing this research,” is securing funding.

The authors state that Dr. Haricharan has a “provisional patent for using DNA repair genes as a biomarker for patient outcome.”

Additionally, author Dr. Stephen J. Freedland is a consultant for Pfizer, Janssen, AstraZeneca, Merck, and Clovis.