Racial disparity in breast cancer mortality linked to genes

Findings of a large, multi-institutional breast cancer study could lead to more personalized risk assessment for women of African heritage and hasten approaches to diagnosing aggressive breast cancers early and treat them effectively. While the odds of developing breast cancer are nearly the same in white and black women, black women are 42% more likely to die from the disease.

The study, published online May 4, 2017, in JAMA Oncology, was designed to understand the racial disparity in survival rates by beginning to unravel the germline genetic variations and tumor biological differences between black and white women with breast cancer.

“People have long associated breast cancer mortality in black women with poverty, or stress, or lack of access to care, but our results show that much of the increased risk for black women can be attributed to tumor biological differences, which are probably genetically determined,” says study author Olufunmilayo Olopade, MD, professor of medicine and human genetics at the University of Chicago.

“The good news,” she says, “is that as we learn more about these genetic variations, we can combine that information with clinical data to stratify risk and better predict recurrences – especially for highly treatable cancers – and develop interventions to improve treatment outcomes.”

“This is a great example of how team science and investments in science can accelerate progress in identifying the best therapies for the most aggressive breast cancers,” says co-author Charles Perou, PhD, a member of the University of North Carolina Lineberger Comprehensive Cancer Center and professor of genetics, and pathology & laboratory medicine at the UNC School of Medicine.

“In the largest dataset to date that has good representation of tumors from black women, we did not find much difference between the somatic mutations driving tumors in black and white women,” he says. “Yet, black women were more likely to develop aggressive molecular subtypes of breast cancer. Now we provide data showing that differences in germline genetics may be responsible for up to 40% of the likelihood of developing one tumor subtype versus another.”

The study used DNA data collected from 930 women-154 of predominantly African ancestry and 776 of European ancestry-available through The Cancer Genome Atlas (TCGA), established by the National Cancer Institute and the National Human Genome Research Institute. Researchers combed through the data methodically, looking for racial differences in germline variations (normal DNA), somatic mutations (tumor acquired), subtypes of breast cancers, survival time, as well as gene expression, protein expression and DNA methylation patterns.

The crucial long-term benefit of this study, according to Olopade, is that “it is a step toward the development of polygenic biomarkers, tools that can help us better understand each patient’s prognosis and, as we learn more, play a role in choosing the best treatment.”

Genes matter, she says. “This is a foot in the door for precision medicine, for scientifically targeted treatment.”

Managed care executives need to learn how to do population risk stratification so they can get better outcomes for ALL patients-black and white, Olopade adds. “It is no longer acceptable to see the widening disparities in survival among black and white and not develop interventions to reduce it.”

Breast cancer is not one disease, and it impacts women differentially, she says. “We now have very effective treatment for the most aggressive breast cancers, and we should make sure all patients benefit from genomic testing. We also need to make sure that women get the right treatment at the right time based on their level of risk. We can no longer practice as if one size fits all.

“Managed care should cover genetic testing and comprehensive risk assessment at diagnosis and promote accurate diagnosis to get the best therapies for (their) enrollees. (They) should promote access to clinical trials. It pays high dividend to get it right and not have to treat advanced cancers.”