Genetic Testing for Cancer Risk

What is genetic testing for cancer risk?

Genetic tests that assess for cancer risk check your DNA for genetic mutations (changes). If the test detects a mutation, this means you’re at increased risk of developing certain types of cancer.

Your genes contain the instructions that tell cells how to grow, multiply and eventually die. With cancer, gene mutations turn healthy cells into cancer cells. The cells grow out of control and form tumors that can spread.

Most cancer-causing mutations aren’t hereditary. But about 5% to 10% of all cancers involve a genetic mutation a person inherits from a biological parent. During genetic testing for cancer risk, a healthcare provider tests your body fluid (usually blood or saliva) for one or more of these hereditary mutations.

But having a cancer-related mutation doesn’t mean you will get cancer. It just means you’re at increased risk. A genetic counselor can advise you on what your test results mean for your health.

What cancers can be caused by a hereditary mutation?

Many different types of cancer can be caused by a hereditary mutation. The most common include:

• Breast cancer
• Colon cancer
• Kidney cancer
• Ovarian cancer
• Pancreatic cancer
• Prostate cancer
• Stomach cancer
• Thyroid cancer
• Uterine (endometrial) cancer

But genetic tests that evaluate risk don’t detect cancer itself. Instead, they check for specific mutations that sometimes lead to cancer. Researchers have identified over 400 genes related to hereditary cancer. They fall into three general categories, including mutations involving:

• Tumor suppressor genes. These genes put the brakes on cancer cell growth. But mutations can allow cancer cells to multiply unchecked. Common types include the BRCA and P53 genes.
• Proto-oncogenes. These genes help cells grow at a normal pace. But when they mutate, they become oncogenes that drive cancer growth. Most oncogenes are acquired, but some are inherited.
• DNA repair genes. When working correctly, these genes fix mistakes in DNA that can lead to cancer. But mutations can prevent them from making repairs.

When is this test performed?

A healthcare provider may recommend genetic cancer testing if your medical history (or your family’s) suggests you may have a hereditary mutation that increases your cancer risk.

You may need genetic testing for cancer risk if you:

• Have several different types of cancer
• Were diagnosed with cancer at a young age
• Have cancer that’s uncommon in people your age or sex
• Develop cancer in both sets of an organ, like cancer in both kidneys or breasts
• Have signs or symptoms linked to certain inherited cancer syndromes (For example, neurofibromatosis Type 1 also causes noncancerous tumors called neurofibromas.)
• Are a member of a racial or ethnic group that’s known for having certain inherited cancer syndromes AND you have additional risk factors

You may need genetic testing for cancer risk if any of the following apply to your family history:

• Several family members have the same type of cancer.
• Several family members had cancer at a young age.
• Several relatives on one side of your family have the same cancer type.
• Family members are known to carry an inherited cancer-related mutation.

Knowing which relatives’ medical histories matter when it comes to your cancer risk can be confusing. Generally, providers consider you at increased risk if a first-degree relative (biological parents, siblings or children) has or had cancer. But in some cases, providers recommend testing if more distant relatives have a cancer history.

Talk to a healthcare provider or a genetic counselor if you’re unsure about whether you’d benefit from genetic testing.

How does the test work?

The test will examine one or more of your genes to check for hereditary cancer-related mutations. Types include:

• Single mutation. This test looks for changes in a specific area of a single gene. Healthcare providers typically test family members when someone in your family has a known specific genetic mutation.
• Single gene testing. This test looks at the entire DNA sequence within a specific gene.
• Panel tests. These tests look for mutations in several genes. In September 2023, the U.S. Food and Drug Administration (FDA) approved a test that can detect the most common hereditary mutations (across 47 genes) with just one blood sample.

What should I expect before the test?

Genetic counseling is the first step in genetic testing for cancer risk. Trained genetic counselors typically discuss:

• Whether genetic testing is right for you.
• What test is most appropriate and how it will work.
• The potential pros and cons of genetic testing.
• What test results may mean for your health.
• How expensive the test will be (including whether insurance will likely cover it).
• How your results may impact you and your family.

What should I expect during the test?

In genetic testing for cancer, healthcare providers typically collect a sample of your blood or saliva that they send to a laboratory. At the lab, technicians look for changes in your genes. The technicians then send the test results to your provider.

There are at-home tests where you collect your saliva and mail it to a lab for genetic testing. But they don’t always provide a complete and accurate picture of how your genes relate to cancer risk. Also, your healthcare provider is bound by a law called the Health Insurance Portability and Accountability Act (HIPAA) to protect your privacy. The companies that sell at-home tests don’t have to follow the same law.

This is why it’s important to speak to a provider or genetic counselor to learn whether you need a genetic test and, if so, which type of test you need.

What should I expect after the test?

Most people receive their test results within two to three weeks. While giving blood takes little time, the technicians may need days or weeks to complete a thorough test analysis.

What results would I get from genetic testing for cancer?

Genetic test results for cancer risk fall into three broad categories:

• Positive. The test found a genetic mutation that’s linked to a specific inherited cancer. It means you’re at increased risk of developing that cancer.
• Negative. The test didn’t find a mutation associated with a hereditary cancer. A “true negative” means there’s a known mutation in your family, but you don’t have it.
• Variant of uncertain significance (VUS). The test found a mutation, but it’s not one that’s associated with increased cancer risk. It may be a benign (noncancerous) variant, or it may be a cancer-related mutation scientists haven’t identified yet.

What are the next steps?

A genetic counselor will review your test results with you. If your results are positive, you might discuss:

• Changes to your care plan, like additional screenings you may need to catch cancers early. You may discuss things you can do to reduce your cancer risk.
• Family planning, including the likelihood of passing the mutation onto a biological child.
• What results mean for your blood relatives, including what steps they should take based on your results.

If your results are negative or VUS, you may still need more frequent check-ups with your provider or follow-up testing. For example, your provider may contact you if additional research identifies a link between a VUS and a specific inherited cancer.

What comes next depends on your unique health history and test results.

What are the benefits of genetic testing for cancer?

Genetic tests can reliably find hereditary mutations that may increase your cancer risk. Genetic testing for cancer risk can help:

• Relieve anxiety or fear of the unknown.
• Provide information you can use to reduce your cancer risk.
• Provide information your healthcare provider can use to catch cancer early.
• Inform your decision-making around having biological children.
• Inform your family members about how genetics may impact their health.

What are the disadvantages of genetic testing for cancer?

This type of genetic testing may cause psychological distress (like anxiety and guilt) and affect family relationships. For example, learning that a mutation runs in your family may feel like an unpleasant burden to bear.

Talking with a genetic counselor can help with processing feelings like these. It can help you communicate more effectively with family members about steps they may need to take to assess their health risks.