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What is genetic testing?

Maybe you’ve heard about genetic testing for diseases and wondered: What does that mean? Should I do it? What do the results mean? Here’s what you need to know.

For example, you may be familiar with women who are at risk for or have breast cancer getting tested for genes called BRCA1 and BRCA2. “It may sound like they are getting tested to see if they have BRCA1 and BRCA2 — but everyone has these genes,” says Monique Lubaton, MGC, CGC, cancer genetic counselor for LifeBridge Health. “The genetic test actually determines if the BRCA1 and BRCA2 genes have mutations.” In other words, if the test is positive, it means that mutations are present.

However, only about 5-10% of all cancer is due to an inherited gene mutation, so these mutations are rare.

What is a mutation?

A mutation is when a gene changes. Genetic mutations can be hereditary or happen randomly.

Non-hereditary genetic mutations can by caused by things like:

  • Hormones
  • Obesity
  • Radiation
  • Smoking
  • Sun
  • Unhealthy diet

What does it mean when you have a mutation?

Let’s go back to BRCA1 and BRCA2. A genetic test determines if one (or, rarely, both) of these genes have mutations. If these genes are damaged, a person is up to 80% more likely to get breast cancer. Why? As a tumor suppression gene, the BRCA gene’s job is to stop cells from growing and dividing rapidly. Therefore, if it has a mutation, cells can develop into cancerous tumors. “There’s no foot on the brake,” says Lubaton.

So what does it mean for you if you test positive? Genetic test results, such as the discovery of mutations on BRCA1 and BRCA2, are complex and many factors must be considered. A genetic counselor can interpret the results, explain them to you and discuss your options. For example, if you need treatment, genetic information can help make your treatment more effective. There are even new medicines that target certain types of mutations.

Who should get genetic testing?

Lubaton says that there are a few “red flags” to keep in mind:

  • 3 or more relatives (on the same side of the family) with the same cancer
  • Early age of cancer onset (50 years old or younger) for the patient or family
  • A personal or family diagnosis with a “rare” cancer with a known genetic tendency, such as ovarian or male breast cancer

Additionally, genetic testing can help people who have cancer learn why they developed it and if they are at risk for other types. This information is also important for their family members, who may be at risk themselves. However, testing may not be helpful for people who are not considered high risk.

How can you get genetic testing?

Work with a genetic counselor

You can meet with a genetic counselor to discuss your personal and family history. If you are a candidate for testing (determined by guidelines and insurance), then your blood will be sent to a reputable clinical genetic laboratory. Once those results are back, the genetic counselor will discuss the results with you.

Use an over-the-counter test

Over-the-counter tests have become popular, but Lubaton says that people should be cautious about their use.

For example, one over-the-counter test only looks for only 3 out of 1,000 known mutations in BRCA1 and BRCA2, which are common in the Ashkenazi Jewish population. These tests also only do one type of imprecise analysis (called genotyping), but a clinical lab test does two types of analysis that are much more accurate.

When the results of an over-the-counter genetic test come in, people might misunderstand the results, and come to incorrect conclusions, both positive and negative. “It is important to know that even if you test negative for a gene mutation, it doesn’t mean that you won’t get cancer,” says Lubaton. Also, because science is evolving, knowledge about genes and treatments is changing and a person might base their own conclusions on information that is not current. “Direct-to-consumer testing is not comprehensive if you want to learn accurate risks about disease,” says Lubaton.

The bottom line

Genetic testing is as complicated as genes themselves. If you think you should be tested or learn more about it, you should speak with a genetic counselor.

If you are concerned about your personal or family history of cancer, a genetic counselor at the Alvin & Lois Lapidus Cancer Institute can review this history, explain hereditary cancer syndromes in greater detail and discuss the benefits and limitations of genetic testing. For more information, call 410-601-5085. Referrals can be faxed to 410-601-4601.