About the Study
About 10 to 15% of triple-negative breast cancers in Caucasians test positive for mutations in the BRCA1 gene. In the African American population, about 35% test positive.
Until recently, BRCA1 was the only gene linked to TNBC. In the past, researchers weren’t able to find other breast cancer risk genes, because the technology was too complicated to check the genes in large numbers of people, Couch says.
“We used to check one gene at a time, which was very time consuming. But about 4 or 5 years ago, sequencing technology changed dramatically, so now we’re able to do these gene panels and check many genes at a time.”
Couch and his research team used a technology called multigene panel testing on blood samples taken from people with triple-negative breast cancer. The technology looks at multiple genes at once, looking for mutations that could be linked to breast cancer.
The team studied how often mutations occurred in people with TNBC compared with a control group of people who didn’t have cancer. This was the first study to find mutated genes that are linked to an increased risk for TNBC. They are: BARD1, BRCA1, BRCA2, PALB2, and RAD51D.
Women who carried any of these gene mutations had a more than 20% lifetime risk for any type of breast cancer. By comparison, women in the general population have about a 12% —or 1 in 8—lifetime risk of getting breast cancer.
“That means,” Couch says, “doctors should consider that women who have any of these mutations will have an increased risk for triple negative breast cancer. Also if a woman with breast cancer has one of these mutations, her doctor may need to consider using specific treatments.
The team was not able to learn why African American women have an increased risk for TNBC, and they suggest that larger studies with African American patients be done.
The team also found strong support that 3 other mutated genes (BRIP1, RAD51C, and RAD51D) moderately increase the risk for TNBC, when they were previously thought to only be associated with ovarian cancer.