Family history, genes and cancer risk
Cancer cannot be passed from a parent to their child (inherited). But genes are passed from parent to child when a sperm and egg join and start forming a baby (conception).
Genes are the instructions inside the cells of our bodies. A change in a gene can mean it does not give the correct instructions to the cell. This type of change is called a gene variant or a gene mutation. Find out more about genes, gene variants and inheritance in our information about acquired and inherited genes.
Gene variants that increase cancer risk
Some gene variants are linked to a higher risk of certain types of cancer. For example, people who have a change in the BRCA1 or BRCA2 gene may have a higher risk of breast, ovarian and some other types of cancer.
Gene variants that increase a person’s cancer risk are also called:
- pathogenic variants
- disease-causing variants
- cancer gene variants
- clinically actionable variants.
When cancer runs in families
It is possible for a cancer gene variant to be inherited by several people in the same family. Because of this, the family may have more cases of certain types of cancer than you would usually find in the general population. This is called a familial or hereditary cancer syndrome.
Experts think inherited gene variants cause less than 5 to 10 in 100 cancer cases (5 to 10%). In fact, the numbers are much lower than this for many cancer types. Lifestyle factors such as smoking or being overweight are more likely to cause cancer.
If you inherit a cancer gene variant from one of your parents, it does not mean you have cancer or will definitely develop cancer. More damage to cells in your body needs to happen before cancer can develop. The inherited gene variant may allow this damage to build up faster. This means that your risk of certain cancers is likely to be higher than someone without that gene variant.
Booklets and resources
If a family is affected by a cancer gene variant, there may be a pattern of cancers 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 1 primary cancer – this means they have had cancer twice, not that cancer has spread to another part of the body.
Some gene variants are linked to several types of cancer. A family with this type of variant may be affected by a group of different cancers. The most common patterns where cancers happen together are:
Some cancer gene variants are more common in certain ethnic groups. For example, families from a Central or Eastern European or Ashkenazi Jewish (Central or Eastern European Jewish) background are more likely to be affected by certain gene variants.
Most of us have relatives who have had cancer. This does not always mean there is a cancer gene variant in your family or that you have a much higher risk of cancer. Most cases of cancer are not caused by an inherited gene variant.
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.
Your GP will use the information about your family to assess your risk of cancer. If they think there is a chance cancer may run in your family, they can refer you to a genetics specialist. This is a doctor or other professional who helps to diagnose, manage, predict and screen for genetic disease.
The genetics specialist will check whether you are likely to have a higher-than-average risk of certain types of cancer. They may offer you genetic counselling to help you understand the cancer risks in your family. They can also tell you whether genetic testing is possible and useful in your situation.
The genetics specialist will explain whether you have a high risk of developing a certain type of cancer. This may be because:
- genetic testing shows you have a gene variant that increases your cancer risk
- the pattern of cancer in your family may be caused by an unknown cancer gene variant
- the pattern of cancer in your family may be caused by a combination of lower-risk inherited gene variants.
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
This type of surgery is usually only offered to people with a very high risk of cancer. It involves removing tissue that is at risk of developing cancer. For example, risk-reducing breast surgery means removing healthy breast tissue to reduce the risk of breast cancer.
Surgery greatly reduces the risk of cancer, but it does not get rid of it completely. Surgery also has risks and possible side effects. It is important to understand these before deciding whether to have this treatment.
If you decide to have risk-reducing surgery, you may also need to decide at what age to have it. Your genetics specialist can explain more, based on the type of gene variant you have and the ages your family members developed cancer. In general, the younger you are when you have risk-reducing surgery, the more likely it is to prevent cancer.
This is also called chemoprevention. It means using drugs to reduce the risk of certain types of cancer. For example:
- anti-oestrogen tablets can help reduce a very high risk of breast cancer
- aspirin may reduce the risk of bowel cancer for people with Lynch syndrome.
Risk-reducing drugs may cause side effects. Occasionally, they may cause serious complications. It is important to discuss the benefits and disadvantages with your doctor.
If you know you have an increased risk of cancer, you may be able to join a clinical trial. Some trials look at genetic causes of cancer or ways of preventing it. Taking part in this type of cancer research is your decision. Ask your genetics specialist for more information.
Having a healthy lifestyle
Having a healthy lifestyle can reduce your risk of cancer. It can also improve your general health and well-being. Your genetics specialist, GP or practice nurse can give you more information about diet and weight, physical activity and other factors such as smoking and sun safety. The World Cancer Research Fund has more information about healthy lifestyle choices to reduce your risk of cancer.
Planning a family
If you have an inherited cancer gene variant, there is a 1 in 2 (50%) chance that any child you have could inherit it from you. Your genetics specialist can talk to you about this if you have questions. Sometimes tests and fertility treatments can be used to ensure a parent’s gene variant is not passed to a child. The Human Fertilisation & Embryology Authority (HFEA) and Genetic Alliance UK have information about this.
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 free on 0800 808 0000, or share your thoughts with members of our Online Community.
We have more detailed information about:
- Inherited bowel cancer
A small number of bowel cancer cases are linked to genetic conditions that can run in families.
- Inherited breast and ovarian cancer
Breast and ovarian cancer can sometimes be linked to gene changes that 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 variants in the BRCA1 or BRCA2 genes can cause a higher risk of some cancers. This includes breast cancer, ovarian cancer, prostate cancer and pancreatic 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 bowel cancer and some other cancers, including womb cancer.
- Multiple endocrine neoplasia (MEN)
MEN1 and MEN2 are conditions that can run in families. These increase the risk of developing some non-cancerous (benign) tumours or cancer in glands such as the thyroid.
Below is a sample of the sources used in our family history and cancer information. If you would like more information about the sources we use, please contact us at firstname.lastname@example.org
Monahan KJ, Bradshaw N, Dolwani S, et al. Guidelines for the management of hereditary colorectal cancer from the British Society of Gastroenterology (BSG)/Association of Coloproctology of Great Britain and Ireland (ACPGBI)/United Kingdom Cancer Genetics Group (UKCGG). Gut. 2020; 69: 411–444. Available from DOI: 10.1136/gutjnl-2019-319915 (accessed October 2022).
NICE. Familial breast cancer: classification, care and managing breast cancer and related risks in people with a family history of breast cancer. Clinical guideline [CG164]. Last updated: 20 November 2019. Available from https://www.nice.org.uk/guidance/CG164 (accessed October 2022).
NICE. Molecular testing strategies for Lynch syndrome in people with colorectal cancer. Diagnostics guidance [DG27]. Published: 22 February 2017. Available from https://www.nice.org.uk/guidance/dg27 (accessed October 2022).
NICE. Testing strategies for Lynch syndrome in people with endometrial cancer. Diagnostics guidance [DG42]. Published: 28 October 2020. Available from https://www.nice.org.uk/guidance/dg42 (accessed October 2022).
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Marc Tischkowitz, Reader and Honorary Consultant Physician in Medical Genetics.
Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.
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