Genetic Testing for Inherited Cancer Risk

Most cancers are not inherited. The American Cancer Society estimates that only about 5 to 10 percent of cancers are passed down from a parent to a child. These inherited changes can raise the chance of certain cancers.

Genetic testing for inherited cancer risk looks for those specific changes. It usually uses a sample of blood or saliva. That works because an inherited change is present in every cell of the body.

This kind of testing can help people understand their risk and plan screening or prevention. But it is not right or needed for everyone.

Genetic testing for inherited risk looks for changes you were born with. These are sometimes called germline changes, mutations, or pathogenic variants.

This is different from testing a tumor to guide treatment. Tumor testing looks at changes that happened during a person's life. It can sometimes pick up inherited changes, but it does not replace testing for inherited cancer risk.

Inherited-risk testing asks one question: were you born with a change that raises your cancer risk?

Cancer can seem to run in a family for many reasons, including shared habits like tobacco use. Genes are not the only cause. But certain patterns make an inherited change more likely. A doctor or genetic counselor may suggest testing when there is:

• A relative with a known inherited gene change that raises cancer risk
• Cancer diagnosed at a young age (for example, colon cancer before 50)
• Several relatives with the same type of cancer
• Certain cancer combinations in a family, such as breast and ovarian, or colon and endometrial
• Rare cancers, such as breast cancer in a man
• Cancer in both of a pair of organs, such as both breasts

Some diagnoses also lead to a testing recommendation, such as ovarian, pancreatic, or triple-negative breast cancer. When possible, testing often starts with a family member who has had cancer.

Testing is most informative for people with a history that hints at an inherited pattern.

A genetic counselor or doctor usually reviews your personal and family history first. If testing makes sense, a small sample is sent to a lab. Most often that is blood or saliva. Results typically come back in about 2 to 3 weeks.

Often the lab runs a panel test, which checks several genes at once. If a specific change is already known in the family, the test may look just for that change.

Results generally fall into three groups:

• Positive. A harmful change was found. This can raise the risk of certain cancers. It may guide earlier or more frequent screening, prevention steps, or treatment choices. It does not mean cancer is certain. Some people with a harmful change never develop cancer.
• Negative. No harmful change was found. This is most reassuring when a specific family change is known and you did not inherit it. That is called a "true negative." If your family's cause is unknown, a negative result does not rule out risk from your history.
• Variant of uncertain significance (VUS). A change was found, but there is not yet enough data to know if it matters. Most are later reclassified as harmless. Until then, decisions are based on your history.

A result is a piece of the picture, not a verdict. Its meaning depends on your family history too.

Testing can offer real benefits no matter the result:

• Peace of mind if you did not inherit a known family change
• A chance to plan screening or prevention if a harmful change is found
• Information that helps relatives understand their own risk
• Guidance for treatment if you already have cancer

There are also downsides to weigh:

• Emotional stress from learning about increased risk, for yourself or family
• Uncertainty from a VUS result
• Cost, if not fully covered
• Privacy considerations

There is no single right choice. It depends on your history, your feelings, and your goals.

Genetic results usually become part of your medical record. A federal law called GINA stops health insurers and most employers from using genetic information to discriminate. It does not cover life, disability, or long-term care insurance, and it does not apply to the military. A genetic counselor can walk you through what is and is not protected.

Some companies sell genetic tests direct to consumers. These often do not check for every important change, and they are not always meant for medical decisions. For example, the only FDA-approved at-home test for inherited cancer risk checks for just three BRCA changes. It misses most harmful BRCA variants. Genetic counseling helps make sure the right test is done and the results are understood.

• NCI — Genetic Testing for Inherited Cancer Risk
• American Cancer Society — Understanding Family Cancer Syndromes