Genetic changes and cancer

Your body is made up of tiny building blocks called cells. Inside every cell is a set of genes. They are the instructions the cell needs to work properly. Sometimes the structure inside a gene is permanently changed, so the gene no longer gives the correct instructions. This change is called a gene mutation.

Some cells in your body develop gene mutations during your lifetime. These are called acquired mutations. It is also possible to have a gene mutation because it passed from one of your parents to you. This is called an inherited mutation.

Eventually, gene mutations in a cell may mean the cell stops working normally. Cancer develops when cells like this can multiply in an abnormal way and grow out of control.

Diagram of cells forming a tumour

Does cancer run in families?

Some inherited mutations make a person more likely to develop certain types of cancer. This means a gene mutation that is linked to cancer may run in a family.

If you inherit a gene mutation like this from one of your parents , it does not mean you have cancer. More damage (acquired mutations) still needs to happen before a cancer can develop. The inherited gene mutation may allow this damage to build up faster.

You might hear different names for the inherited mutations that make cancer more likely. These include:

  • inherited cancer genes
  • cancer predisposition genes
  • cancer susceptibility genes.

 

Family history and cancer risk

If a family is affected by a gene mutation, there may be a pattern of cancers diagnosed in that family. For example, there may be:

  • several people who have the same types of cancer
  • people who were younger than usual when they were diagnosed.
  • someone who has had more than one primary cancer. This means they have had cancer twice, not that one cancer has spread to another part of the body.
  • a family history of certain cancers and the family is from an Eastern European or Ashkenazi Jewish (Eastern European Jewish) background. Some inherited cancer genes are more common in these ethnic groups.

Genetic testing for cancer risk

If you are worried about the pattern of cancer in your family, talk to your GP. They will ask you about any close blood relatives who have had cancer. Close blood relatives are your parents, brothers, sisters, children, aunts, uncles and grandparents. People you are related to by marriage are not blood relatives.

It is important to remember that cancer is very common. Most of us have relatives who have had cancer. This does not always mean there is a cancer gene in your family, or that you have a much higher risk of developing cancer. Most cases of cancer are not caused by an inherited mutation. Only a small number of people get cancer that is clearly linked to an inherited cancer gene.

Your GP will use the information about your family to assess your risk of cancer. If your GP thinks there is a chance that cancer may run in your family, they can refer you to a genetics specialist.

The genetics specialist will check whether you are likely to have a higher than average risk of certain types of cancer. They can also tell you whether a genetic test is possible and useful in your situation. We have more information about seeing a genetics specialist and having genetic testing.

The genetics specialist will explain if you have a high risk of developing a certain type of cancer. This may be because:

  • you had a genetic test that found an inherited cancer gene
  • the pattern of cancer in your family is likely to be caused by an unknown inherited cancer gene
  • you have a genetic condition that increases your risk of cancer (see ‘More information about genetic conditions and inherited cancers’ below).

It is natural to want to know what is likely to happen, so you can plan for your future. Family history and genetic testing only let us estimate levels of risk. It does not tell us who will definitely get cancer or when they will develop it.

Hearing you have a higher risk of cancer can come as a shock. Some people feel like they are being told they already have cancer. Others find that knowing the result helps them make choices to reduce their risk.

Managing genetic cancer risk

Your genetics specialist will give you information about reducing your risk of cancer. Depending on the type of cancer and your level of risk, they may give you information about the following.

  • Cancer screening tests

    You may be offered screening tests to find or prevent a type of cancer developing. Screening looks for early signs of cancer or for changes that happen before a cancer develops. There are different screening tests for different types of cancer.

  • Risk-reducing surgery

    Some people with a high cancer risk decide to have risk-reducing surgery. This means removing the tissues that are at risk of getting cancer. For example, risk-reducing breast surgery means removing healthy breast tissue to reduce your risk of breast cancer. This type of surgery is usually only offered to people with a very high risk, such as people who have inherited certain cancer gene mutations. Surgery greatly reduces the risk of cancer, but it does not get rid of it completely.

  • Risk-reducing drugs

    Certain drugs may be used to reduce the risk of certain types of cancer. Some women who have a high risk of breast cancer may take anti-oestrogen tablets to reduce their risk. People with Lynch syndrome may take aspirin to reduce their risk of bowel cancer developing. Risk-reducing drugs may cause side effects and occasionally may cause serious complications. It is important to discuss the benefits and disadvantages with your doctor.

  • Clinical trials

    If you know you have an increased risk of getting cancer, you may be able to join a clinical trial. These look into genetic causes of cancer or ways of preventing it. Taking part in a clinical trial is completely up to you. Ask your genetics specialist for more information.

  • Healthy lifestyle

    There is not always clear evidence about how a healthy lifestyle affects cancer risk in people with a family history of cancer. But there is strong evidence it improves your general health and well-being. Your genetics specialist, GP or practice nurse can give you more information about healthy living.

  • Talking to children

    Most inherited cancer genes do not increase the risk of cancer until adulthood. Usually, children in families with these types of cancer gene wait until they are older to think about genetic testing. This can make it harder for parents to decide when to tell them there is an inherited cancer gene in the family. We have more information about talking to children about cancer risk.

  • Planning a family

    If you have an inherited cancer gene, there is a 1 in 2 (50%) chance that any child you have could inherit it from you. We have more information about planning a family if you have an inherited cancer gene.

If you are struggling to cope with a high risk of cancer, talking about your feelings and worries may help.

You can get support from your genetics specialist or your family and friends. You can also talk to our cancer support specialists on 0808 808 00 00, or share your thoughts with members of our Online Community.

More information about genetic conditions and inherited cancers

We have more detailed information about:

  • Inherited bowel cancer
    A small number of bowel cancer cases are linked to genetic conditions which can run in families.
  • Inherited breast and ovarian cancer
    Breast and ovarian cancer can sometimes be linked to gene changes which can run in families.
  • Other inherited conditions that increase cancer risk
    Some rare conditions which run in families can increase the risk of some cancers.
  • BRCA1 and BRCA2 gene mutations
    Changes in the BRCA1 or BRCA2 genes can cause a higher risk of breast, ovarian and some other types of cancer.
  • Familial adenomatous polyposis (FAP)
    FAP is a condition that can run in families. If not treated, FAP causes a high risk of bowel cancer.
  • Lynch syndrome
    Lynch syndrome is a condition that can run in families. It increases the risk of developing some cancers.
  • Multiple endocrine neoplasia (MEN)
    MEN1 and MEN2 are conditions that can run in families. These syndromes increase the risk of developing some benign tumours or cancer in different glands, such as the thyroid. 

How we can help

Macmillan Cancer Support Line
The Macmillan Support Line offers confidential support to people living with cancer and their loved ones. If you need to talk, we'll listen.
0808 808 00 00
Every day 8am - 8pm
Email us
Get in touch via this form
Chat online
Every day 8am - 8pm
Online community
An anonymous network of people affected by cancer which is free to join. Share experiences, ask questions and talk to people who understand.
Help in your area
What's going on near you? Find out about support groups, where to get information and how to get involved with Macmillan where you live.