Genetic testing for inherited cancer genes

Genetic testing can be used to look for inherited gene mutations that raise the risk of cancer in a family.  A genetic counsellor can tell you if a test may be possible and useful in your situation. 

For example, if you: 

  • have a close blood relative who had a genetic test that found an inherited cancer gene 
  • you have a cancer that is likely to be linked to an inherited mutation - the results of genetic testing may affect other people in your family.

How is genetic testing done?

There are usually 2 steps to genetic testing.

Usually, a person in the family who has had cancer is tested first. If a cancer gene mutation is found, other members of the family can have predictive testing.

Sometimes there is no living relative with cancer who can be tested first. You may still be offered a genetic test if:

  • the pattern of cancer in your family strongly suggests there could be a gene mutation
  • you have a family history of cancer and you are from an Eastern European or Ashkenazi Jewish (Eastern European Jewish) background – some inherited cancer genes are more common in these ethnic groups.
  • Mutation search

    This is also called diagnostic testing. First, the laboratory looks for the gene mutation that may run in your family. They do this on a blood sample from someone in your family who has had cancer. It usually takes up to about 8 weeks to get the results. The test may:

    • find a cancer gene mutation
    • not find a cancer gene mutation
    • find a variant of uncertain significance (see below).
  • Predictive testing

    If the mutation search finds a cancer gene mutation, other family members can then be tested for the same mutation. 
    A predictive test is faster than a mutation search. This is because the laboratory knows which gene change to look for and where to find it.

Genetic testing in children

Most inherited cancer genes do not cause cancers in children so they are not usually tested. Once they become adults, they can make their own decisions about testing.

A child may be tested if there is a chance they have a gene mutation that causes health problems before adulthood. For example, a condition called familial adenomatous polyposis (FAP) causes growths in the bowel (polyps). These usually start to appear when a person is in their teens.

Other rarer conditions where children are tested for inherited gene mutations include:

  • the multiple endocrine neoplasia (MEN) syndromes MEN1 and MEN2
  • Von Hippel-Lindau syndrome (VHL)
  • Li-Fraumeni syndrome.

Children affected by these conditions have a higher risk of cancer and other health problems before they are adults.

Before having genetic testing

Your genetics specialist will explain what to expect. There may be several things to think about before you decide to have a genetic test.

Possible advantages

  • The test may show you do not have the gene mutation and that your cancer risk is low. You will not need to consider extra screening or risk-reducing treatments. You will know you cannot pass on the cancer gene to any children you have.
  • If you find out you have a gene mutation, this may help you decide how to reduce your cancer risk. Your options may include screening to find a cancer early, treatments to reduce your risk of getting cancer and making lifestyle changes.

Possible disadvantages

  • If you find out you have a gene mutation, you may feel more worried about getting cancer.
  • Tests do not always give clear answers. Some people find out they have a change in a gene, but it is not known how this affects their cancer risk. Doctors call this a variant of uncertain significance (see below).
  • Even if testing does not find a gene mutation you may be told you have a raised cancer risk. This is because your family history may still show that an unknown gene mutation is likely.
  • If you find out you have a gene mutation, you will need to decide whether or how to tell other family members this may affect.

Your test results

Your genetic specialist will tell you when you are likely to get your test results. You may feel anxious about getting your results. It can help to have someone with you for support and to help you to remember what was said.

If a cancer gene is found

This means you have inherited a gene mutation that increases your risk of getting some cancer types.

Other members of your family

If you have an inherited cancer gene, this may affect other people in your family. You may have to decide if and how to tell them.

Your genetics specialist may give you a letter you can give to family members. It will help explain your results and what it may mean for them. They can then decide whether they also want to have genetic counselling and predictive testing. Their GP can refer them to their nearest genetics clinic or family cancer centre.

Your feelings

Talking about an inherited cancer gene with your family can be difficult. People may have questions that you cannot answer or have feelings you did not expect.

It is important to remember that no one is to blame for the genes they inherit or pass on. People with a gene mutation sometimes have feelings of guilt, blame or responsibility. But we cannot control the genes we pass on.

If there are children in your family, we have more information about talking to children about an inherited cancer gene.

Your genetics specialist can help you talk through your feelings. You can also talk to our cancer support specialists on 0808 808 00 00 (Monday to Friday, 9am to 8pm).

If a cancer gene is not found

The mutation search may not find a cancer gene.

This can happen even if you have a strong family history of cancer. It may be that:

  • the cancers in the family are not due to an inherited cancer gene - they may have happened by chance or for other reasons we do not understand 
  • there is a gene mutation in the family, but it is not one we currently know about or test for routinely
  • there are several ‘lower-risk’ genes in the family – these, together with environmental factors, can still increase the risk of cancer.

Your feelings

You may have mixed feelings if you are told the test has not found a gene mutation.

You may feel relieved an inherited cancer gene has not been found. But it also means you cannot know for certain if cancer is an inherited problem in your family.

Your genetics specialist may explain you still have a higher risk of cancer based on your family history. This means the pattern of cancer in your family is unusual and may be caused by an unknown gene mutation.

You may be offered extra screening or risk-reducing treatments. Because you have less clear information about your risk, it may be more difficult to decide what you want to do.

You may decide to reduce your cancer risk and improve your health in other ways. This may include giving up smoking, eating a healthy diet and being more physically active.

Variants of uncertain significance (VUS)

Sometimes the mutation search finds a gene mutation that has not been clearly linked to cancer. Doctors call this a variant of uncertain significance. This means it is not clear whether the gene mutation is the cause of the cancer.

Because of this, the genetics specialist cannot offer predictive testing to other people in the family. They may ask for blood samples from them to try to get more information. These extra tests may help them decide if the gene mutation is the reason for the pattern of cancer in the family.

The family may also be asked to keep in contact with the genetics clinic. This is in case they find out more about the gene in future.

Confidentiality and genetic testing

Your doctor and genetic specialist cannot tell anyone you have had a genetic test. And they cannot tell the results of your test unless you agree to this.

When they take your blood for the genetic test, they may ask if they can also take a sample for research. This may help scientists to find other cancer genes in the future. They are not given your personal details.

If you are worried about your personal details and confidentiality, talk to your doctor or nurse. They will explain how your information is used and protected.

Insurance and genetic testing

Some people worry insurance companies will refuse to insure them or will charge more if they have a genetic test. There is no law to prevent this. But for now, the Association of British Insurers (ABI) and the government have agreed how an insurer can use the results of genetic testing. This is called the Concordat and Moratorium on Genetics and Insurance.

The agreement lasts until 2019. It may change after that. It only covers genetic testing. It is not about your personal or family history of cancer. Insurance companies may still ask questions about your and your family’s health, and any cancer diagnoses.

The agreement says an insurer will not ask you to take a genetic test. Sometimes they will ask for the results of genetic testing you have already had.  If you do not have cancer, they will not ask for results of genetic tests for inherited cancer genes.

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