Genetic Testing for Cancer Risk

What is genetic testing for cancer risk?

Genetic testing can assess your cancer risk by looking at your DNA for genetic mutations. Genetic mutations are inherited (hereditary) changes in your DNA sequence that may mean you are at an increased risk of developing genetic conditions like cancer.

Our genes contain instructions which tell our cells how to grow, multiply and die. Genetic mutations can cause healthy cells to turn into cancer cells, which grow in an uncontrolled way and form tumors.

Most mutations that cause cancer aren’t hereditary, but up to 10% of cancers are thought to be caused by a genetic mutation that is inherited.

Having a genetic mutation linked to cancer risk doesn’t mean that you will go on to develop cancer. It means that you are at an increased risk. Genetic counseling will be offered before genetic testing so that the results and what they mean for your health, are fully explained.

There are many different types of cancer-causing mutations, but the most common include the BRCA and P53 genes.

How is genetic testing performed?

A genetic test is a simple test that involves taking a small sample of blood (or saliva). Your genes will then be checked for one or more cancer-related hereditary mutations.

Before genetic testing for cancer, you will be offered genetic counseling, where a trained professional will discuss whether testing is right for you, the pros and cons of testing, and what the results may mean for you and your family.

Which cancers are associated with inherited genetic mutations?

Many types of cancer are associated with an inherited genetic mutation, including:

• Breast cancer
• Colorectal cancer
• Endometrial cancer
• Kidney cancer
• Ovarian cancer
• Pancreatic cancer
• Prostate cancer
• Stomach cancer
• Thyroid cancer

Which genes are associated with hereditary cancer risk?

Genetic testing looks for specific mutations that can lead to cancer. There are thought to be over 400 genes that are related to hereditary cancer. These genes fall into three main categories:

• Tumor suppressor genes: These genes prevent the growth of cancer cells, but a mutation can stop them from working properly, allowing cancer cells to multiply. The BRCA gene and P53 gene are examples of tumor suppressor genes.
• DNA repair genes: These genes fix mistakes in our DNA that could lead to cancer. A mutation in a DNA repair gene stops these repairs from happening.
• Proto-oncogenes: These genes make sure our cells grow at a normal rate. A mutation in a proto-oncogene turns it into an oncogene, which can drive the growth of cancer.

Who should have genetic testing for cancer risk?

Your doctor may recommend genetic testing for cancer risk if you or your family’s medical history indicates a hereditary mutation that may increase the risk of cancer. It may also be recommended if:

• You had cancer at a young age
• You have had several types of cancer
• You have had a cancer that is uncommon in your age group or gender
• You have symptoms associated with inherited cancer syndromes
• Several family members have the same cancer type
• Several family members were diagnosed with cancer at a young age
• Family members carry an inherited cancer-related mutation

A genetic counselor can help you to decide whether genetic testing for cancer risk would be of benefit to you.

What are the possible results from genetic testing for cancer risk?

There are three main categories of results:

• Positive: A genetic mutation was found that is linked to a certain inherited cancer; therefore, you are at an increased risk of developing that type of cancer.
• Negative: No mutations were found that are associated with hereditary cancer.
• Variant of uncertain significance: This means a mutation was found but it is not known whether the mutation is associated with cancer risk.

A genetic counselor will discuss the results with you in detail. If your result is positive, they may recommend additional screenings designed to catch cancer early. Lifestyle changes will also be discussed, which can reduce cancer risk. The impact on your family will also be discussed.

The exact next steps will depend on your test results and health history.