One in five black women with breast cancer were found to have inherited mutations on at least one of 18 genes linked to the disease, in a study that may explain the earlier onset and more-aggressive malignancies in that group.
Researchers from the University of Chicago used genome sequencing to study the DNA of 249 black women, 56 of whom had at least one mutation that mattered for their cancer, according to a study presented at the American Society for Clinical Oncology’s meeting in Chicago.
Breast cancer is the most common malignancy among black women, and they are 40 percent more likely than white women to die from the disease, according to the U.S. Centers for Disease Control and Prevention. Even accounting for differences in education and wealth, black women have worse outcomes in cancer, previous studies have shown.
“This is an understudied and under-tested population, and this study underscores what you don’t know can hurt you,” said Andrew Seidman, a professor of medicine at Weill Cornell Medical College in New York. He wasn’t involved in the study. “The woman who doesn’t get tested and doesn’t know her risk may not pursue preventive strategies,” such as mastectomy, he said.
The women were considered to be at a higher risk of carrying a mutation than the general black population and were referred for genetic counseling. Even so, the rate of mutations was surprisingly high, since only 5 to 10 percent of breast cancers in the general population are expected to have a hereditary aspect.
Mutations were found on BRCA1 and BRCA2, two mutations that confer a 60 percent risk of breast cancer. Mutations were most prevalent among women with triple-negative breast cancer, in which the three most common types of receptors known to fuel malignant growth aren’t present. A third of those women had at least one mutation.
Another 27 percent of patients who carried mutations were young, or diagnosed with the disease before the age of 45. So were half of the women who had a second unrelated cancer in the breast.
The majority of mutations weren’t uniform, and weren’t seen more than once in the group, the authors said. The finding suggests that black women should be genetically screened more often for breast cancer than white peers, especially if they are diagnosed with cancer young, have triple-negative breast cancer, or have a family history of the illness. The study underscores the need for broader genetic screening among understudied ethnic groups.
The study was funded by the National Institutes of Health, the Breast Cancer Research Foundation, and Komen for the Cure.