Predictive genetic testing and cancer

Your mom was diagnosed with breast cancer in her 40s. What does her diagnosis mean for you? Are you more likely to develop breast cancer? Should you consider predictive genetic testing?

The short answer is maybe. There’s a lot to consider before making this important decision. Such testing looks for inherited gene mutations that may increase your risk for developing certain cancers. It’s typically an option when certain types of cancer run in your family and a gene mutation is suspected.

You may want to pursue predictive genetic testing based on your personal or family history of cancer, which may include having:

• First-degree relatives (parents, siblings or children) with cancer
• Multiple relatives on one side of your family with a history of the same cancer
• A family member who has had more than one type of cancer or cancer diagnosed at a younger age than is typical for that cancer (usually age 50 and younger)
• Family members whose cancers were linked to a single gene mutation, such as BRCA1 or BRCA2, or who have close relatives with a history of cancers linked to hereditary cancer syndromes, such as Lynch syndrome, a common cause of hereditary colon cancer (If you have Lynch syndrome, you’re more likely to develop colorectal cancer and/or other cancers at a younger age.)
• A generation-to-generation pattern of cancer in a family
• One or more people in your family who underwent genetic testing and had a mutation

Your ethnic background is another factor to consider when thinking about predictive genetic testing. For example, Ashkenazi Jewish people are at higher risk of having a BRCA1 or BRCA2 mutation.

If something is found during an exam that’s indicative of an inherited cancer—such as having multiple colon polyps—your doctor may suggest predictive genetic testing as well.

Even if you check off one or more of these boxes, the American Society of Clinical Oncology recommends predictive genetic testing only if there’s an accurate test available and actionable steps that may be taken based on the results, such as more frequent screenings and/or other risk-reducing strategies.

In other words, you shouldn’t dive headfirst into predictive genetic testing. You should meet with a genetic counselor first to discuss your risks, as well as the pros and cons of testing for your particular situation so that you can make an informed decision about what steps are best for you. This relationship doesn’t end here either. A genetic counselor may help you understand the results of your test and discuss any next steps. The results may change the trajectory of your cancer screenings, and may mean more medical tests as well to help you stay a step ahead of a cancer diagnosis.

Types of predictive genetic testing

There are more than 50 named hereditary cancer syndromes, such as Lynch syndrome, and most may be caused by a single genetic mutation. In addition, there are other genes that aren’t associated with named syndromes, but do increase cancer risk, such as:

• Inherited mutations in PALB2, which is associated with an increased risk of breast and pancreatic cancer 
• CHEK2, which is linked to higher risk of breast and colon cancer 

Some tests look for mutations in a single gene, while others look for mutations in multiple genes at the same time (panel testing).

A small sample of blood, saliva, cells from inside your cheek, or even skin cells are taken and sent off to a specialized laboratory for analysis. This process may take a few weeks or longer.

At-home testing

When it comes to home-based tests: buyer beware. These tests ask you to send a sample of saliva for analysis to a given company that then sends you back your results, including whether or not you have certain genes that may affect your risk of cancer or other conditions. Such tests typically have more limited ability to detect inherited cancer risks, and results may need to be confirmed by another laboratory.

Predictive genetic testing for cancer or other diseases should only be done after consulting with a genetic counselor or genetics specialist and through a licensed health-care facility and lab.

What do the results mean?

A positive result means you have a mutation in a gene (or genes) that increases your risk of developing a certain type or types of cancer. A negative result means that no mutations were detected, which can reduce but not eliminate the chances of an inherited risk for cancer. Genetic test results may be inconclusive, meaning a difference or change was found in a gene but the impact on cancer risks are unknown.

Keep in mind: Although a genetic test may reveal you have a genetic mutation that increases your risk of a certain cancer, it can’t say with certainty that you will develop the cancer.

Other factors that increase cancer risk include:

• Smoking
• Eating lots of red meat and processed foods
• Consuming too much alcohol
• Tanning in the sun without adequate protection
• Exposures to certain chemicals, pesticides and radiation in the environment

If you test positive for a genetic mutation linked to cancer, it may affect other family members, too. Your genetic counselor will help you navigate sharing the news and other decisions based on results.

Insurance

Some insurers cover the cost of certain predictive genetic tests. Genetic counselors help people to determine whether medical and insurance criteria for genetic testing are met, and can provide information about potential costs for the genetic testing.

Federal laws have been passed to protect you from health insurance and employment discrimination based on genetic test results. These laws do not provide protection in the areas of life or long-term care insurance or disability. These topics, as well as the privacy laws about how genetic information is stored and can be released, should be considered before having genetic testing.