Mutations in Susceptibility Genes Common in Younger African American Women with Breast Cancer

A high percentage of African-American women with breast cancer who were evaluated at a university cancer-risk clinic were found to carry inherited genetic mutations that increase their risk for breast cancer.

The finding suggests that inherited mutations may be more common than anticipated in this understudied group and may partially explain why African-Americans more often develop early onset and “triple-negative” breast cancer, an aggressive and difficult-to-treat form of the disease.

It also demonstrates the potential benefits of increased access to genetic counseling and testing for women with breast cancer and their close relatives. Through these services, family members who are found to share the same genetic risk factor for breast cancer can be offered personalized strategies for early detection and prevention of breast cancer.

“Our study confirms the importance of screening for mutations in breast cancer susceptibility genes in all African-American breast cancer patients diagnosed by age 45, those with a family history of breast or ovarian cancer, or with triple-negative breast cancer before age 60,” said study author Jane Churpek, MD, assistant professor of medicine at the University of Chicago Medicine.

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The study, to be presented June 3 at the 2013 Annual Meeting of the American Society of Clinical Oncology in Chicago, is the first comprehensive screening among African-American women of all 18 known breast cancer susceptibility genes using new methods called targeted genomic capture and next-generation sequencing. The researchers found that 56 of the 249 women studied (22 percent) at the University of Chicago Medicine’s Cancer Risk Clinic had inherited at least one damaging mutation that increased their risk of breast cancer. {snip}

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Whereas 12 percent of women in the general population will develop breast cancer by age 80, those carrying a harmful mutation in BRCA1 or BRCA2 have a 37 to 85 percent lifetime risk of developing breast cancer. Mutations in these genes provide the best tools for tailoring risk-reducing interventions.

The authors caution that the patients in this study are not a typical cross-section of African-American women. Two-thirds of them were referred to the cancer-risk clinic for genetic evaluation, often due to a family history of breast cancer. Not all of them, however, had this significant risk factor. Forty percent of the 249 patients had no family history of breast or ovarian cancer, yet the researchers found damaging mutations in 12 percent of those patients.

“We expected the women in our study to have a higher risk of carrying an inherited mutation than typical breast cancer patients,” Churpek said, “but some of their risk factors — diagnosis by age 45 or triple-negative breast cancer — also are more common among African-American women.”

Once diagnosed with breast cancer, African-American women have lower survival rates. Regional variations in survival suggest that much of the difference may be driven by reduced access to screening and optimal care, but there is mounting evidence, including this study, that differences in tumor biology, such as a higher rate of inherited mutations in genes that increase the risk of aggressive forms of breast cancer, also play a role. In those cases, delay of diagnosis can prove deadly.

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