BRCA1 and BRCA2 Gene Mutations: The Basics

August 24, 2020 5:00 AM

A genetic counselor discusses the impact of these mutations and the importance of collecting family histories.

genetic testing DNA chromosomes in blue
Graphic: Stephanie King

This article is the final piece of a three-part conversation on BRCA1 and BRCA2 gene mutations. Read BRCA1 and BRCA2 Gene Mutations: I Know I Have Cancer, What Good is Testing? and BRCA1 and BRCA2 Gene Mutations: I Have a Mutation, What Are My Options?

Mutations in the BRCA1 and BRCA2 genes are linked to the development of breast cancer, ovarian cancer and other types of cancer.

Genetic testing and counseling services can determine whether a person carries these mutations and, if they do, how the information could help inform cancer prevention or treatment decisions.

In the first of a three-part conversation, Kara Milliron, a genetic counselor at the University of Michigan Rogel Cancer Center's Breast and Ovarian Cancer Risk Evaluation Clinic, discusses some of the ins and outs of BRCA gene mutations.

Both the BRCA1 and BRCA2 genes, which we all carry, play a role in making sure cells grow at the proper rate.

“They act like a brake on a car,” Milliron explains. “When there is a change or a mutation in BRCA1 or BRCA2, those genes don't work properly, and that's where we see an increased risk for developing cancer.”

These mutations can be passed down in families. Inherited susceptibility, which includes BRCA1 and BRCA2, are responsible for about 5% to 10% of breast cancers and 20% of ovarian cancers.

“That’s why it’s important to know your family history,” she says. “We encourage people to try to go back three generations — back to your grandparents.”

Genetic counselors are on the lookout for clues in family histories that may indicate an increased risk of carrying a mutation in a cancer susceptibility gene, such as cancers that occur before the age of 50, or the occurrence of more rare cancers, such as ovarian cancer, fallopian tube cancer, primarily peritoneal carcinomatosis, pancreas cancer and male breast cancer.

“When we see breast and ovarian cancer in the same individual, or when we see a rare type of melanoma called ocular melanoma, that makes us a little bit concerned about an inherited susceptibility,” Milliron says. “So, there are some clues that we see in the family history that make us a little bit more suspicious that there may be a gene change that's being passed on in the family.”

While BRCA1 and BRCA2 mutations are most frequently talked about in relation to breast and ovarian cancers, it’s important to know that they’ve been linked to other types of cancer as well, Milliron stresses.

“Men in particular are somewhat forgotten with regards to these two genes because the cancer risks or the cancer burden is lower in men — but it does have significant consequences, if a man does carry a BRCA1 or BRCA2 gene mutation,” she says. “They have a higher risk for developing prostate cancer and those prostate cancers tend to be more aggressive.”

Genetic testing is recommended where there’s a family history of aggressive prostate cancers with a Gleason score of seven or higher. And for men diagnosed with one of these aggressive prostate cancers or with metastatic prostate cancer.

"You should also know that if you do get tested, your results won’t be shared with anyone — and in fact there are laws that prohibit genetic testing from being used in a discriminatory manner."
Kara Milliron, M.S., C.G.C.

Test results may help inform treatment decisions as well as highlight potential risk in other family members, she says.

“So, with BRCA1 and BRCA2 I really think that we need to expand the focus beyond breast and ovarian cancer,” Milliron says. “If you have a family where there's not a lot of women and the gene mutation is being passed on through the dad's side of the family, sometimes those families can be missed because we're focusing so much on breast and ovarian cancer that we don't pick up the clues of the prostate cancer, or the uncle with pancreas cancer, or the uncle that had no cancer diagnosis, but their children may have had very aggressive prostate cancers. So, we really need to make sure that we look at both sides of the family — and that we look at three generations, at grandparents, parents, aunts, and uncles, and also cousins.”

Patients should also be aware that most insurance carriers cover genetic testing, and when they don’t, the out of pocket cost is usually around $250, Milliron adds.

People also express concerns that the results of genetic testing could somehow be used against them in the future, she notes.

“You should also know that if you do get tested, your results won’t be shared with anyone — and in fact there are laws that prohibit genetic testing from being used in a discriminatory manner,” Milliron says.