How genetics affects your cancer risk—and what you can do about it

May 5, 2025

Editor’s note: The information in this blog refers to hereditary genetic testing only, which is different from tumor testing (also known as molecular profiling). Hereditary genetic testing is typically performed using DNA isolated from normal blood or saliva cells to identify genetic mutations (also called pathogenic variants) that may increase that person’s risk for cancer. Genetic testing may have implications both for a person and their family members. Tumor testing is done after a cancer diagnosis using DNA isolated from tumor cells to identify mutations that may affect how the patient responds to certain treatments.

Would you be surprised to hear that only 5%-10% of cancers are hereditary? That means that most often, cancer is not caused by having a family history of the disease. It’s one of the reasons why dépistages systématiques du cancer are so important for everyone. But, if you do have a personal or histoire de famille of cancer or certain other diseases, your genetics could increase your cancer risk. Understanding your genetic makeup can help you take proactive steps to reduce or even remove that increased cancer risk for you and your family. Here’s what you should know—and how to find out if genetic testing is the right option for you:

What is genetics?

Genetics is the study of genes. Our bodies are made up of cells and genes are the instructions for how our cells work. They are the fundamental units of heredity passed along from parent to child that determine our physical and biological characteristics. Genes are made up of DNA and our DNA is exactly the same in every cell of our body.

How do my genes affect my cancer risk?

Some genetic variants in your genes that function to defend against cancer could impact your cancer risk by altering the normal function of these genes. These are called genetic mutations (also known as pathogenic variants).

It’s important to remember that each of us has millions of variants in our DNA, but only a very small number of them are associated with an increased risk for cancer. Having a genetic mutation does not mean that you will go on to develop cancer, just that you are at an increased risk for cancer. Similarly, not having a genetic mutation does not mean you will not go on to develop cancer, it just means that you are not at increased risk for cancer due to genetics as compared to the general population.

What is genetic testing?

Genetic testing can be performed by testing a person’s blood or saliva to determine whether they have inherited a genetic mutation in any of the genes known to be associated with an increased risk of cancer. Ideally, genetic mutations are found before any other signs of disease, which means you could know if you are at increased risk of cancer before it develops so you can take action for better health outcomes.

Genetic testing is just the first step.

Depending on what you learn from genetic testing, you may be able to take preventive measures that allow you to reduce the risk of developing certain hereditary cancers or identify cancer at its earliest and most treatable stage. Your provider may give you different screening recommendations, which could include getting screened earlier, more often or by a different method than those at average risk.

What are some of the most common genes associated with an increased risk for cancer?

Two of the most recognized genes are BRCA1 et BRCA2, also known as the “BRACA” genes. Mutations in these genes can significantly elevate a person’s risk of sein cancer and ovarian cancer, and to a lesser extent, prostate cancer and pancreatic cancer.

Mutation in another 50-100 genes are also known to increase the likelihood of breast, colorectal or prostate cancers, and other cancers as well.

Why should I have genetic testing done?

Vous voudrez peut-être envisager des tests génétiques si :

Multiple members of your family following the same lineage have been diagnosed with cancer.

Some of your family members were diagnosed with cancer at unusually young ages for their specific cancer types.

There is a history of cancers in your family that are often associated with gene mutations, such as breast, pancreatic, or ovarian cancers (or some rare cancer types such as adrenocortical carcinoma, medullary thyroid cancer, or paragangliomas or pheochromocytomas). You will especially want to consider genetic testing if these cancers have been diagnosed in several close relatives (parents, children or siblings).

A family member has undergone genetic testing and identified a gene mutation.
You are of Ashkenazi Jewish descent, in whom 1 in 40 individuals may carry a BRCA or other gene mutation.

How do I get genetic testing?

If you are thinking about genetic testing, consult with a genetic counselor or a health care provider who specializes in cancer genetics. They will review your overall health and risk factors, including your family history, and explain the advantages and disadvantages of genetic testing. They will also discuss the potential outcomes of the test, including psychological risks and benefits, and guide you on your options after testing.

Before scheduling a meeting with a genetic counselor or health care provider, it’s important to check with your insurance company to determine if the consultation and/or genetic testing are covered by your plan.

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Experts say that depending on the genetic test you get, you may consider getting re-tested about every 10 years. While your genome doesn’t change, there are continued breakthroughs in genetics that can expand testing panels and look for newly discovered mutations that can impact your cancer risk.

What about direct-to-consumer tests?

Direct-to-consumer tests have been popular in recent years. These tests can be done at home by providing a saliva sample and sending it back to the company’s lab for analysis. While these tests are primarily used to find family connections or discover one’s ancestry, several do have health-based genetic testing components.

If a direct-to-consumer test does identify a genetic mutation, you should speak with a genetic counselor about next steps, which may include additional testing.

If a direct-to-consumer test does not identify a genetic mutation, you should also speak with a genetic counselor about next steps, which may include repeat testing to confirm results.

While the relative accessibility of direct-to-consumer tests may make it the first step in someone’s exposure to their genetic data, experts recommend meeting with a genetic counselor when considering genetic testing. Given the complexities involved, genetic counseling plays a crucial role in the genetic testing process.

Remember, genetic testing—regardless of the result—does not take the place of dépistages systématiques du cancer.

Knowing your family health history can help determine your personal cancer risk, and genetic testing may be an option to help you prevent cancer or detect it early, when treatment is more likely to be successful. But keep in mind that testing is just the first step on the road to prevention and wellness for you and your family.

For more information on genetic testing, visit preventcancer.org/genetics.