Decoding genetic testing and breast cancer


by Vaishali Kent, MD

Oct 4, 2023

All humans’ genetic makeup is 99.9% identical.

That 0.1% of genetic variation is responsible for differences in our eye color, height and even cancer risk.

Breast cancer is one of the cancers that can be linked to your genes. To have inherited breast cancer means that a person received a mutated gene from their mother or father, and that mutated gene is the cause of their breast cancer. Many people assume the majority of breast cancers are passed down through genes, but in fact only 5-10% of breast cancers are truly inherited.

Thanks to recent advances in technology, you can now undergo genetic testing to determine if you have inherited a mutated gene that can elevate your risk of developing breast cancer.

When is genetic testing for breast cancer helpful?

Genetic testing can be helpful if you have a family history of cancer, particularly a history of breast or ovarian cancer. When you know this information, you can make informed health decisions and implement lifestyle changes to reduce the risk of developing cancer in the future. You can increase screening for cancer so it can be detected early or take preventative measures to prevent the cancer from occurring.

Genetic testing can highlight mutations such as the BRCA1 gene. People who inherit certain BRCA1 mutations have a higher likelihood of developing breast and ovarian cancer in their lifetime compared to those without these mutations.

Tennis player Chris Evert’s sister died from ovarian cancer that doctors later discovered was linked to a version of a BRCA1 gene. Chris underwent genetic testing herself and was found to carry the same mutation. In a courageous decision, she opted to remove her ovaries. During this procedure and subsequent results from the surgery, it was discovered that Chris had already developed stage 1C ovarian cancer. Had she waited, she may have had a much worse outcome. She is now cancer free.

If you do not have a family history of the disease and you have been diagnosed with breast cancer, it’s more likely caused by environmental factors, lifestyle choices or age rather than an inherited genetic component. Genetic testing can provide peace of mind for individuals with a family history of breast or ovarian cancer.

What steps do you need to take to decide if genetic testing is right for you?

I recommend the following steps if you have a family history of breast cancer or an early-onset, aggressive breast cancer.

Talk to your physician at a genetic counseling appointment

The first step to deciding if genetic testing is right for you is to talk to your physician.

Your surgeon or oncologist will guide you through a genetic counseling appointment to help you make your decision. They will know your family history and disease progression and can offer advice based on your individual needs.

Additionally, in this appointment, I advise my patients on the potential risks of genetic testing.

Unfortunately, if genetic testing shows you have a mutation that could lead to cancer, life insurance companies can legally deny you from taking out a life insurance policy. We also know that genetics is an evolving science and results can change as more information is made available.

Discuss the decision with your family

Talk to your family about the risks and benefits of genetic testing. Your genetic information is closely linked to your family, so they may want to know what steps you are considering taking.

Talk to your doctor about ordering the genetic test

I recommend that patients use a diagnostic genetic testing service rather than a commercial at-home testing service. Direct-to-consumer DNA testing is not thoroughly regulated and can be sold to individuals without any independent analysis to verify the claims or results. These tests have a 40% false positive rate and negative results are not definitive. At-home testing services are not accurate for guiding medical decisions.

Your physician will refer you to a trusted diagnostic testing service with experienced genetic counselors. Here, they will take a blood or saliva sample for testing.

Plan for next treatment steps with your physician

The results of your genetic test will help your surgeon make the best decision for you. Depending on the results, your surgeon may recommend lifestyle changes, increased screening or prophylactic surgery. Prophylactic surgery, also known as preventive surgery, is a medical procedure that removes healthy tissue or organs that are likely to develop cancer. This type of surgery's main purpose is to reduce the risk of future health problems.

Talk to your family about the results

I have many breast cancer patients who are concerned about their children and grandchildren’s risk of developing breast cancer. The results of the cancer patient’s genetic test will either give their family members some peace of mind or prepare them for their own potential risk.

If you have an inheritable breast cancer mutation like BRCA1 or BRCA2, it does not automatically mean your children will inherit it.

Even if your children do inherit a BRCA1 or BRCA2 gene, the likelihood the mutation will turn into cancer varies from person to person, and even from family to family.

Although genetic testing does not always provide absolute clarity, it is an incredibly useful tool in the management of cancer. If you have questions about breast cancer and genetic testing, find a breast surgeon or oncologist near you.

About the Author

Vaishali Kent, MD, is a breast surgeon on the medical staff at Baylor Scott & White All Saints Medical Center – Fort Worth.

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