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.”
Sanford Burnham Prebys
Dr. Svasti Haricharan
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.
University of Illinois Cancer Center
Dr. Kent Hoskins
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.