The study, published in Jama Oncology, is one of the first to connect genetics to racial difference in breast cancer diagnosis and found that black women are more likely to get forms of highly aggressive breast cancer.
The results from the study could lead to more personalized risk assessment for black women and speed up the development of ways to diagnose specific types of aggressive breast cancer earlier and treat them effectively.
“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,” said Olopade.
The study compared DNA from 930 women of African and European decent to look for racial genetic differences that could lead to disparities in cancer types and survival rates. They found that the genetic differences found between the two groups could be responsible for up to 40 percent likelihood of developing one type of cancer tumor over another.
Another finding is that black women with hormone receptor positive, HER2-negative breast cancer had a higher risk of breast cancer recurrence than white women. The study also confirmed that black patients were typically diagnosed at a younger age and were more likely to develop more aggressive breast cancer, including triple-negative cancers that lack estrogen and progesterone receptors and HER2.
“Black women in all categories, including the most common breast cancers, were likely to have a worse prognosis,” Olopade said.
The study also found 142 genes that had different expression levels according to race. One gene, CRYBB2 (Crystallin Beta B2), was consistently higher in tumors from black patients, as well as in normal tissues, suggesting it may be a race-specific gene.
The researchers also found somatic mutations in 13 genes or DNA segments that had different frequency levels in tumors from black and white women. One of them, a mutated gene called TP53, was more common in black women (52%) than white women (31%) and was a strong predictor of disease recurrence.
A crucial long-term benefit of this study, according to co-author Charles Perou, PhD, of the University of North Carolina, will be to “develop better strategies to empower all women, especially black women, to know their genetics and be more proactive in managing their risk,”
Dr. Olopade moved from Nigeria to Chicago in 1983 to complete her residency in hematology and oncology at Cook County Hospital. In 1991 she moved to University of Chicago where she founded The Center for Clinical Cancer Genomics. In 2005 Olopade was granted a McArthur “Genius” Grant of $500,000 for her groundbreaking research and care on the prediction, prevention and early detection of cancer for moderate and high-risk populations, specifically African and African-American women. Today, she is a leading authority on hereditary breast cancer and cancer risk assessment.