African American Women More Likely to Die from Breast Cancer

Several genetic characteristics of more aggressive tumors significantly more prevalent in the African American community.

Researchers at the Massachusetts General Hospital (MGH) Cancer Center have, for the first time, identified genomic differences between the breast tumors of African American women versus white women.

These differences could contribute to the recognized differences in recurrence rate and survival among patients. The researchers report that several genetic characteristics of more aggressive tumors were significantly more prevalent in the African American community and had a greater risk of tumor recurrence.

“In addition to having a higher prevalence of triple-negative breast cancers than Caucasian women — something that has been documented in previous studies – we found that African American women with breast cancer had a significantly higher prevalence of the TP53 driver mutation, basal tumor subtype and greater genomic diversity within tumors, all of which suggest more aggressive tumor biology,” said lead author Tanya Keenan, MD, of the MGH Cancer Center. “The higher risk of tumor recurrence that we observed among African American women was reduced when controlling for those factors, suggesting that these genomic differences contribute, at least partly, to the known racial disparity in the survival of African American and Caucasian breast cancer patients.”

While improved diagnostic and treatment methods have reduced the overall death rate from breast cancer, authors note that this trend has not carried over into the African American patient population. Currently, African American women in the United States who are diagnosed with breast cancer are 40% more likely to die from their disease than are white women.

Socioeconomic factors such as income, health insurance, and access to health services certainly contribute to this issue, but do not account for all the reasons why this disparity continues to be recognized. It has been previously acknowledged that more aggressive triple-negative breast cancer occurs more frequently in African American women, but no previous study has examined racial differences in tumor genotype and how they might contribute to the risk of cancer recurrence.

Researchers analyzed whole-exome sequencing data from the tumors of 664 white patients and 105 African American patients who were diagnosed between 1988 and 2013. Although the same 5 tumor-specific mutations were most prevalent among both groups, African American patients’ tumors were driven by the TP53 mutation, while the PIK3CA mutation was more common among the tumors of white women.

The number of mutations and prevalence of basal-like and mesenchymal stem-cell subtypes was also more prevalent in the tumors of African American patients. Tumor recurrence was faster and more likely among African American patients, particularly for basal subtype tumors or those driven by the TP53 mutation.

“Our study adds important pieces to the puzzle of why African American women with breast cancer are less likely to survive,” said senior author Aditya Bardia, MBBS, MPH, attending physician at the MGH Cancer Center and assistant professor of Medicine at Harvard Medical School. “If our findings are confirmed by additional studies, they may open doors to the development of targeted therapies against the tumor subtypes more likely to affect African Americans and potentially help reduce racial disparities in breast cancer.”