Precision Medicine: How Genetic Testing Is Improving Breast Cancer Treatment and Prevention

Some say knowledge is power. And for some women, this is especially true when it comes to knowing their risk for breast cancer.

Treatment options for cancer in the past were typically a one-size-fits-most approach, but today, thanks to the advent of precision medicine, doctors are able to select more personalized treatments that are more likely to help patients based on their genes and/or the cancer’s genes.

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The use and importance of genetic testing is growing in breast cancer prevention and treatment. Although most people who develop breast cancer have no family history, when a strong family history of breast cancer is found, you can reduce your chances by up to 95% – helping to save your life and potentially the lives of other family members as well.

“Knowing your risk is powerful as it allows for people to have a better understanding of their cancer risks and any screening or preventative measures that are available to them based on these risks,” said Rebecca Luiten, a certified genetic counselor MD Anderson Cancer Center at Gateway Medical Center. “If a mutation is found, patients can then take advantage of increased screening protocols, such as more frequent colonoscopies, or preventative procedures, such as a double mastectomy, to lower their risks.”

If you are considering genetic testing, we share some important information to help guide your decision.

What are BRCA gene mutations?

BRCA1 and BRCA2 are the two most well-known genetic mutations. Everyone is born with BRCA1 and BRCA2 genes, which typically help to prevent cancers. But sometimes, mutations in these genes prevent them from working properly, according to the Centers for Disease Control and Prevention.

“When a person is born with a mutation, or change, in their BRCA1 or BRCA2 gene, the gene is not able to do its job properly to prevent cancer the way it should,” Luiten said. “Because the genes cannot do their job like normal, a person with a mutation in their BRCA1 or BRCA2 gene is at an increased risk for cancer. Inheriting these mutations can put you at greater risk not only for breast, but also ovarian, prostate and pancreatic cancers."

What does genetic testing look at?

There are several tests that look for mutations in the BRCA1 and BRCA2 genes, but the gold standard for genetic testing is to order a multigene panel. While single-gene testing is often used when there is already a known gene mutation in the family, the multigene test looks for mutations in several genes at once.

“In general, most people have testing that looks for mutations in 20 to 50 genes, but depending on family history, more genes will sometimes be ordered,” Luiten said. “It's also important to remember that there are thousands of mutations and markers in each gene, but some at-home, or direct-to-consumer, tests only look at 3 mutations total, so be aware.”

Of the more than 1,000 BRCA mutations, there are many BRCA mutations that would not be detected by at-home tests. If you take one of the at-home tests and your results are negative, don’t assume you aren’t at risk. You might have a type of BRCA mutation that the at-home test does not detect. It’s best to share these results with your doctor to discuss next steps.

Is the genetic test painful?

A genetic test is actually painless and quite simple. It typically involves giving a blood or saliva sample.

Am I a good candidate for genetic testing?

If you have a personal or family history of cancer at a young age (less than age 50) or have a family history of three or more relatives with the same type of cancers, you may wish to consider genetic testing. In addition, if you have a personal or family history of ovarian, pancreatic or aggressive prostate cancer, you should also consider genetic testing.

Depending on your answers, your doctor may suggest you speak with a genetic counselor or a physician who is an expert on genetics about genetic testing.

“Genetic counseling is recommended for those undergoing genetic testing because it gives patients the necessary education needed to decide if genetic testing is a good fit for them,” Luiten said. “It allows patients to ask all the questions they have, discuss the pros and cons to testing and whether it is a good fit for that patient or not.”

Genetic counselors are trained to discuss psychosocial concerns that focus around genetic testing, like how to inform family members or how to deal with potential anxiety from these results. Genetic counselors are also up to date on new advancements in genetics, so utilizing a genetic counselor ensures you access the most accurate and complete testing.

What do the results mean?

Each gene has slightly different cancer risks and recommendations, so knowing can give you a better understanding of your cancer risks and any screening or preventative measures that are available to you based on these risks. It also allows your doctor to tailor treatments and medical recommendations.

“For example, if a person is found to have a BRCA1 gene mutation, we know that their lifetime risk for breast cancer is up to 87%, and we should recommend additional breast screening with an MRI in addition to a mammogram at minimum, but sometimes the option for a double mastectomy as a preventative surgery is available to patients as well,” Luiten said.

Are there any risks with genetic testing?

“There are few harms related to having genetic testing for cancer risks,” Luiten said. “In the past, genetic testing was very expensive, and people were discriminated against. Thankfully this has changed.”

So far, discrimination hasn’t proven to be a major problem. In 2008, the Genetic Information Nondiscrimination Act was signed into law protecting most Americans against discrimination based on their genetic information when it comes to health insurance and employment.

Genetic testing has also become more affordable. If you meet some of the features mentioned above in your or your family’s history, genetic testing is often covered by insurance and most patients will pay less than $100 to get testing done.

Some patients also express anxiety over finding out if they have tested positive for a mutation, but the involvement of a genetic counselor can help a patient deal with this anxiety.

If I do genetic testing, do I still need regular mammograms?

Yes. Mammograms are currently the only screening test that has been proven to reduce breast cancer deaths. Don’t delay being screened.

“This benefit was shown through multiple randomized clinical trials, the most rigorous type of medical research trial to directly prove the benefit of a test or treatment,” said Vilert Loving, MD, chief of breast imaging in Arizona. “As a result, MD Anderson continues to recommend annual screening mammograms starting at age 40. For women at high risk due to genetic mutations, screening at a younger age should be considered. The exact starting age may vary, and genetic counselors can help women develop a screening plan that is specific to their risk level.” 

When is a breast MRI used?

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With some genetic mutations, such as BRCA1 and BRCA2, research suggests that mammograms may not be enough. If you have been recently diagnosed with breast cancer or are at higher risk for breast cancer, you may benefit from a breast MRI for more detailed pictures of the inside of your breast.

“Breast MRI has been shown to better detect cancers at an earlier stage in high-risk women,” Dr. Loving said. “Therefore, women with high-risk genetic mutations may benefit from annual MRI exams in addition to mammograms.”

Is a genetic test right for you?

The decision to undergo genetic testing is very personal, so there is no right or wrong choice.  However, if you suspect you might be at higher risk for breast cancer, speak with a genetic counselor or genetic specialist to decide if it’s the right fit for you.