What is genetic testing for breast cancer?

Genetic testing for breast cancer identifies inherited gene mutations. If these mutations are present, a person has a very high risk of developing breast cancer. They also indicate a higher risk of ovarian cancer and certain other cancers, such as aggressive prostate cancer in men and pancreatic cancer. About 5 to 10% of breast cancers in the United States are due to an inherited gene mutation. There are two main breast cancer (BRCA) genes that account for about half of these cancers—BRCA1 and BRCA2. So people often refer to a breast cancer genetic test as BRCA testing. But there are known mutations in different genes, including PALB2 and others, that can affect your breast cancer risk.

Why is BRCA and other gene testing for breast cancer performed?

Testing for genetic mutations helps people understand their risk of developing breast cancer. It can also tell them about the odds of passing gene mutations to their children. Using the results, people can make informed decisions about managing their risk.

Testing people with breast cancer can also be useful for their own treatment. Research suggests women who have BRCA mutations are more likely to develop second breast cancers. This includes cancers in the same breast and cancers in the opposite breast. Knowing your status can help you make informed treatment decisions.

Most people with breast cancer do not have an inherited genetic link. Because of this, experts only recommend testing for people whose family or personal history suggests a high likelihood of a genetic link. Your doctor may recommend testing if you have:

• Ashkenazi Jewish heritage, which tends to have a higher rate of BRCA mutations
• Blood relative with a known BRCA gene or other gene mutation relating to breast cancer risk
• Female blood relative with multiple breast cancers or breast and ovarian cancer
• Personal history of triple-negative breast cancer before age 60
• Personal or family history of breast cancer at age 50 or younger
• Personal or family history of male breast cancer
• Two or more blood relatives on the same side of the family with breast cancer, ovarian cancer, pancreatic cancer, or aggressive prostate cancer

If possible, it is best for the person with breast cancer to go through testing first. A negative result may mean other family members do not need testing. A positive result means genetic testing could be beneficial for other family members. If it is not possible to know the status of the person with breast cancer, you may still want to pursue testing if your family history suggests a high risk. Your doctor can guide you with the decision.

Who performs genetic testing for breast cancer?

Clinical geneticists and genetic counselors will perform a breast cancer risk assessment. Clinical geneticists are doctors who specialize in hereditary disorders. Genetic counselors are healthcare providers with training in medical genetics and counseling. If you decide to go ahead with testing, a lab technician will perform the actual test. Your primary care doctor or—if you have a cancer diagnosis—your oncologist may be the doctor to order genetic testing based on your individual circumstances, but a clinical geneticist or genetic counselor interprets the results and provides consultation services.

How is genetic testing for breast cancer performed?

The genetic test itself is very simple on your end. It only involves collecting a blood or saliva sample. Your doctor will send the sample to a lab for complete analysis of your DNA.

You may be curious about how accurate genetic testing is with home kits. Beware of these kits. Using them can lead to incomplete information and incorrect results. At-home genetic testing kits are not suitable for fully assessing your breast cancer risk. Also, your health information may not be private. Pay particularly close attention to the kit’s use guidelines and privacy statement.

What are the risks and potential complications of breast cancer genetic testing?

Genetic testing for breast cancer carries little to no medical risk. However, finding out your genetic status can have physical and emotional effects. Positive results can lead to anxiety, depression or anger. Negative results can stir up feelings of guilt when other family members do not have the same results. Even uncertain results can lead to uncomfortable feelings and worry.

If your results are positive, you have decisions to make that will affect you physically. This includes whether or not to have surgery to help prevent breast and ovarian cancers. These surgeries involve removing healthy breasts and ovaries to prevent a disease. However, not everyone with these genetic mutations will develop cancer. So the choice is not easy. What’s more, positive results can also lead to deep questions about having children.

There is also a very small risk of false-positive or false-negative results. While rare, false genetic testing results could potentially mean making major medical decisions using incorrect information. It could also mean a false sense of security when your risk is actually very high.

None of these matters are simple or straightforward. This is one reason it is vital to work with a genetic counselor. Together, you will explore these topics before making a decision about testing. The genetic counselor can help you prepare for your feelings. He or she can also help you think through the actions you would be willing to take with positive results. You may decide you would rather not grapple with these issues. Just because a healthcare provider recommends genetic testing does not mean you have to do it. Ultimately, the decision is yours to make.

How do I prepare for genetic testing?

There is very little you need to do physically to prepare for genetic testing. You can ease the collection process (a blood or saliva sample) by staying hydrated. However, there is a lot that goes into a risk assessment. You will need a complete copy of your medical history, including relevant tests and exams. You also need detailed information about your family’s cancer history. This includes current age and cancer status or date and cause of death for parents, grandparents, siblings, children, and blood-related aunts, uncles, nieces, nephews and cousins. Pathology reports from any blood relative with breast cancer can be very helpful if you have access to them.

What can I expect after breast cancer gene testing?

Knowing what to expect makes it easier to plan and prepare.

How long does genetic testing take?

Once you make the decision to have genetic testing, the test collection takes only a few minutes. However, the results can take about a month.

What do the results mean?

Unfortunately, test results are not always clear. Your genetic counselor or physician will view the results in the context of your whole medical history.

A positive result means the lab found a genetic mutation known to affect breast cancer risk. You carry the gene mutation and have a 50% chance of passing it on to a child. You are also at increased risk for developing breast and ovarian cancers. However, a positive result does not mean you absolutely will develop these cancers.

A negative result means the lab did not find a genetic mutation associated with breast cancer risk. Here are two reasons for this:

• Your negative result is a ‘true negative’ if you have a close blood relative with breast cancer and a known positive result. With a true negative, you do not carry the genetic mutation. Your risk of breast cancer is the same as anyone else in your age group.
• Your negative result is less clear if you do not have the genetic status of a close blood relative with breast cancer. The same is true if testing has not identified any mutations in blood relatives with breast cancer. This is an ‘uninformative negative.’ It means experts can’t fully rule out a harmful mutation. It is possible, though rare, for the test to miss the mutation. It is also possible your family carries a mutation in a gene that scientists have yet to connect with breast cancer risk.

An uncertain result means the lab found a mutation in a breast cancer gene, such as a BRCA1 or BRCA2 mutation, but scientists do not know how it affects breast cancer risk. Other names for this result are ‘ambiguous’ and ‘variant of uncertain significance.’

Your genetic counselor will meet with you to discuss your results. He or she can help you understand what your results mean for your risk. You can also develop a plan to manage your risk. For unclear results, this may mean relying on your family history and other risk factors to make screening or treatment decisions. Rely on your counselor’s expertise and take your time when making decisions about your future.