One in five African-American women with breast cancer may have an inherited mutation in a breast cancer susceptibility gene.
The results of a recent study found that one in five African-American women with breast cancer referred for genetic counseling has an inherited mutation in a breast cancer susceptibility gene. This was 22 percent of women tested.
The study found that the mutations were more prevalent among women with an aggressive form of breast cancer called triple negative, those diagnosed at or before age 45, those who had already had breast cancer, and those with a family history of breast or ovarian cancer. University of Chicago researcher Jane E. Churpek, who announced the findings at the annual meeting of the American Society of Clinical Oncology in early June, says the results suggest that broader screening may be beneficial for these women and their families.
Genomic DNA from 249 unrelated women with breast cancer who identified themselves as African-American was analyzed for the study. Researchers found that 56 of the women had at least one clinically relevant genetic mutation. With only 5 to 10 percent of breast cancers thought to be genetically linked, this high percentage was a surprise to the researchers, but at the same time, many of the women had a family history of breast or ovarian cancer or had developed breast cancer before age 46. The women were tested at the University of Chicago with an assay called BROCA, named after French scientist Pierre Paul Broca, who was one of the first to describe inherited breast and ovarian cancers.
The BROCA assay uses new tools to identify a wider array of genetic changes and can be used clinically to test for mutations in the 18 genes known to increase breast cancer risk. Churpek’s research is the first comprehensive study among African-American women of all known genes associated with breast cancer susceptibility. The study also showed that the majority of the mutations identified were unique to the individual woman. This highlights the genetic diversity in the population and suggested that techniques that can look at all genetic changes will be the most useful for these women.
This study provides additional information concerning why African-American women are more frequently diagnosed with breast cancer at a young age and more often develop aggressive breast cancer. African-American women are known to have higher rates of triple-negative breast cancer, meaning the cancer is not fueled by estrogen or progesterone or overexpresses the oncogene HER2, all of which have specific targeted treatments. This leaves a woman with triple-negative breast cancer relying on traditional chemotherapy.
Sue Friedman, executive director of Facing Our Risk of Cancer Empowered (FORCE), says this study further emphasizes the importance of genetic counseling.
“Twenty percent of the African American women who tested positive for a cancer-causing mutation in this study had a mutation in a gene other than BRCA1 or BRCA2. Genetics experts can evaluate family history and recommend which genetic tests are most likely to provide information about risk. Further, the risks associated with several of these other genes are not as well studied as BRCA1 or BRCA2, so an expert in cancer genetics can best look at the genetic status and family history to provide information about risk for further cancer and risk to family members.”
Churpek says the results emphasize several issues, the first being awareness in the African-American community that women diagnosed under age 46, those with triple-negative breast cancer or those who have close family members with breast or ovarian cancer should be referred for genetic testing. “The key is to better identify who is at risk so we can really begin to focus on prevention,” she says.
“This is especially important because previous studies have shown that African-American women with a family history of breast or ovarian cancer are less likely to undergo genetic counseling than white women with a similar history,” Churpek says. “The reasons for this remain unclear, but we certainly need to focus on improving access to these services especially in underserved communities for whom the availability of the services may be limited.”
The second issue is the testing process, Churpek says. Current clinical testing to look for abnormalities in BRCA1 and 2, which account for the majority of hereditary breast cancers, requires two steps, each with its own significant cost. The first step involves a risk assessment for BRCA mutations, followed by a genetic test. “For some patients, the second step may not always be covered by their insurance, so it limits us from doing the complete test. If testing beyond these two genes is necessary for a patient, there is a further cost.”
This summer the US Supreme Court is deciding whether Myriad, the company that holds the patent on the BRCA mutations and the subsequent genetic test, will retain its patent. If it does not, the number of options for testing could increase and the cost may go down.
Another major challenge to conducting broader screening, Churpek says, comes from the fact that the exact cancer risks associated with each of the less well-known genes on these panels remain to be determined. Therefore, the value of enhanced screening or preventive surgery options are difficult to establish.
While additional information is being studied, Churpek says African-American women diagnosed with breast cancer need to discuss with their doctor their family medical history as well as the details of their breast or ovarian cancer diagnosis, specifically their age at diagnosis and if they had triple-negative breast cancer, to determine if genetic counseling and testing is appropriate.
“Healthy women without a history of cancer should regularly update their doctors. If a close relative newly develops cancer this could affect their own risk of developing cancer, so they should bring this up at their next regular visit so their doctor can use this information to help keep them healthy,” says Churpek.