Understanding Breast Cancer Genes

Mutations in BRCA1 and BRCA2 may increase breast cancer risk in men and women

/ Author:  / Reviewed by: Robert Carlson, M.D Beth Bolt, RPh

Between 5 and 10 percent of breast cancer cases have a genetic basis. While it might be tempting to know whether you have a mutated breast cancer gene, genetic testing is only recommended for people with certain risk factors.

Everyone has BRCA1 and BRCA2 genes — even men. Inherited alterations (mutations) in these genes significantly increase the risk of developing breast or ovarian cancer.

Most people are not candidates for genetic testing. Screening tools help identify people who may have a higher risk of having mutated genes. Genetic testing may be necessary for these people.

Based on the test results, you may need to make important medical decisions. This process requires the skill, knowledge and guidance of a genetic counselor.

Who Should Be Tested for These Genes?

One of the first steps in genetic testing for breast cancer is determining whether a person has a higher risk of having mutated breast cancer genes.

To do this, doctors use a screening tool. The screening tool is a survey about your medical history, particularly as it pertains to breast and ovarian cancer. It also asks questions about cancer in relatives.

The US Preventive Services Task Force lists the following factors that might indicate the need for breast cancer risk screening:

  • Breast cancer that was diagnosed at age 50 or younger
  • Breast cancer in both breasts
  • A family history of breast or ovarian cancer
  • Breast cancer in one or more male family members
  • Ashkenazi Jewish ancestry

The screening tool assesses your risk of having genetic mutations. Doctors use this data to decide whether genetic testing is advisable for you.

"For women it is important to understand their family history of breast cancer," said Graham A. Colditz, MD, DrPH, epidemiologist and associate director for prevention and control at the Alvin J. Siteman Cancer Center, Washington University School of Medicine and Barnes-Jewish Hospital in St. Louis, MO. "Having a clear understanding of mother, grandmother, and aunts history of breast cancer is important to guide the identification of those at high risk of having inherited genes that predispose to the development of breast cancer.

"While there are a number of genetic markers of increased risk, the importance of mother's age at diagnosis is a key part of a full family history. Diagnosis at age 50 or younger significantly increases risk of breast cancer in offspring."

Genetic Testing

A small sample of blood, a swab of cells from inside the cheek or fluid collected from mouth rinsing is all that doctors need to test for BRCA1 and BRCA2.

Currently, only a few highly specialized labs perform genetic testing. Due to the complex nature of the testing, a certified lab should conduct it.

The cost for genetic testing for BRCA1 and BRCA2 varies from several hundred to several thousand dollars, and your insurance company may not pay for any or all of it.

Genetic testing is available for BRCA1 and 2 mutations, as well as other genes associated with an increased risk of breast cancer, such as CDH1, PTEN, RAD51C, STK11 and TP53.

Genetic Counseling: Dealing With the Results

When you consider genetic testing, your doctor will likely refer you to a genetic counselor before you take the test. Your counselor will discuss the risks, benefits and limitations of the testing with you.

Considering these factors can help you prepare for results you might receive and help you decide whether testing is right for you.

Finding mutations in BRCA1 or 2 doesn't necessarily mean you will get cancer. It means your chances are increased.

According to the National Cancer Institute (NCI), women without mutations in breast cancer genes have about a 12 percent risk of getting breast cancer in their lifetimes. These women have about a 1 percent chance of getting ovarian cancer.

By age 70, the NCI estimates that 55 to 65 percent of women with a harmful mutation in BRCA1 will get breast cancer, and 39 percent will get ovarian cancer.

About 45 percent of women with a harmful mutation in BRCA2 will get breast cancer, and 11 to 17 percent will get ovarian cancer by age 70.

Men with mutations in BRCA1 or 2 also face an increased risk of developing breast or prostate cancer, the NCI noted.

After finding BRCA1 or 2 mutations, your doctor may ask you to consider several items:

  • Sharing this knowledge with other family members who may be at risk
  • Risk-reducing surgery, such as removal of one or both breast and/or ovaries
  • Taking medicine to reduce cancer risk
  • Having more frequent or more extensive breast cancer screening
  • The fact that your genetic mutation can be passed to your children

If your testing did not find gene mutations, your risk of breast or ovarian cancer is likely low. However, you could have mutations in genes that were not included in your testing.

"Prevention strategies exist to help women at genetically increased risk," Dr. Colditz told dailyRx News. "Some would argue that the decision to have a test for genetic predisposition should include a clear discussion of the treatment options or prevention actions to be followed if genetic testing shows that risk is increased. Strong evidence shows that bilateral oophorectomy [removal of both ovaries] significantly reduces risk of breast cancer in those with BRCA1 and BRCA2 mutations.

"Likewise, other risk factors for breast cancer, such as late menopause, also increase risk in those with genetic predisposition. Even for women at high risk, prevention offers substantial opportunities to reduce the odds of developing breast cancer."

A genetic counselor or your doctor can help you make sense of the results and what they mean for your health.

A Word About Your Privacy

You might wonder what will happen to your insurance rates if your health insurance company finds out you have an increased risk for cancer, but there's no need to worry.

Federal law prohibits health insurance companies from using your genetic information to decide whether you are eligible for coverage or how much you will pay for that coverage.

Review Date: 
August 8, 2014