If a cancer occurs more frequently in a family than would be expected in the general population, this may be a sign that some people in the family have inherited a cancer susceptibility gene (see our section on cancer and genes for more information).
In many cancers, it’s thought that about 5-10% of cases (between 5 and 10 out of every 100 cases) may be linked to inherited genes.
Scientists have discovered cancer susceptibility genes for some of the more common cancers that can run in families, such as cancers of the breast, bowel, ovary and womb. There are other cancers, such as prostate, pancreatic and testicular, which may run in families, but specific cancer susceptibility genes for these cancers haven’t been identified yet.
Sometimes there are a number of different types of cancers in a family. Usually, these cancers are unrelated and are due to a combination of risk factors such as age, lifestyle and the environment. But in some cases, when certain pairs of cancers run together in a family, such as bowel and womb cancer, or breast and ovarian cancer, it can be a sign of an inherited susceptibility gene.
There are also some very rare inherited gene mutations that increase a person’s risk of getting several different types of cancer at a young age. In families that have these cancer susceptibility genes, several people may be diagnosed with cancer in childhood, adolescence, or in their twenties or thirties. We have information about some of these rare conditions.
Our cancer support specialists can also give you more information about inherited gene mutations and cancer.
If someone has an inherited cancer susceptibility gene, they have a significantly increased risk of developing certain cancers compared with other people in the population. In most cases, people who inherit a cancer susceptibility gene won’t definitely get cancer. You can’t inherit cancer from someone in your family, but you might inherit an increased risk of developing a certain type of cancer.
In many families with higher than expected numbers of cancers, the cancers aren’t caused by a cancer susceptibility gene. It’s thought that for some families, the increased risk of cancer may be caused by several genes which, in combination with lifestyle and environmental risk factors, affect the risk of developing certain cancers. These genes have a weaker effect on the risk of cancer than cancer susceptibility genes, so they are sometimes called ‘low risk’ genes or ‘low penetrance’ genes.
Only a few low penetrance genes have been identified so far, but there aren’t tests available for checking if someone has them. Researchers are trying to find out more about what these genes are, and how, in combination with lifestyle and environmental factors, they might affect an individual’s cancer risk.
If you're worried about your family's history
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You may want to tell your GP if:
two or more blood relatives on the same side of your family have developed the same type of cancer at a fairly young age (under 50)
certain pairs of cancers run together in your family, such as bowel and womb cancer, or breast and ovarian cancer
you have a relative who developed breast, ovarian, bowel or womb cancer at a younger age than usual.
If your GP thinks there may be an increased risk of cancer in your family, they will refer you to a genetic counsellor or a cancer specialist. This could be in a family cancer clinic or a cancer genetics clinic.
You could try to speak directly to a specialist at your nearest family cancer clinic or genetics clinic. However, specialists usually prefer to see people who have been referred by their GP. You can find a list of all genetic centres in the NHS on the British Socitey for Human Genetics website.
Your GP, genetic counsellor or consultant will use a number of criteria in your family history to assess whether there may be an inherited cancer susceptibility gene in your family.
If you’re worried that breast and/or ovarian cancer may run in your family, our online tool OPERA can give you personalised information about your risk, which you might want to take to your doctor to discuss.
OPERA is based on guidance on familial breast cancer from the National Institute for Health and Clinical Excellence (NICE). OPERA isn’t intended to replace professional genetic counselling services, so if you’re concerned about your genetic risk you should still consult your doctor.
When cancer may be linked to an inherited gene
This may be the case if:
there are two or more close blood relatives on the same side of the family affected by the same type of cancer. Close relatives are your parents, children, brothers, sisters, aunts, uncles and grandparents.
a close relative has had more than one primary cancer. This means that they have had cancer twice, but the second cancer was a new cancer (for example, breast and then ovarian cancer) and was not due to the first cancer spreading to another part of the body.
members of your family have had cancer at a young age (under 50).
you have Polish or Jewish ancestry (in these populations, there are certain gene faults that occur more commonly than in the general population).
certain cancers have occurred on the same side of the family. There are two main patterns where cancers occur together (although other very rare patterns of cancers also occur):
- breast and ovarian cancer
- bowel and wom (endometrial) cancer, sometimes with other cancers such as stomach, kidney, ovarian or pancreatic cancer.
'I was given confidence from my OPERA results to ask for the referral I have received.'
The factors listed here can only give an estimate of whether or not a family may have an increased risk of developing cancer.
Every family is different. For example, very small families obviously won’t have a high number of members with cancer. And families with more men than women may not show clear patterns of breast and ovarian cancer.
In cases of adoption, the criteria needs to be used flexibly.
If you have only one elderly relative with breast, bowel or any other cancer, it’s very unlikely that the cancer is hereditary. If there were an inherited cancer susceptibility gene in your family, it’s very likely that more relatives would have been diagnosed with the same type of cancer.
After referral to a genetics clinic
If your GP refers you to a genetics clinic, you’ll probably have to wait for a few weeks or months before you’re seen by a specialist.
It’s important to remember that even if you do have an increased risk, you’re not in immediate danger of developing cancer. Your cancer risk won’t change over a few weeks or months. However, if you’re finding this waiting period difficult, you can contact our cancer support specialists talk it through.
The genetics clinic or family cancer clinic will look at your GP’s referral and information about your family history. They may decide that you’re not at an increased risk of developing cancer after all. The staff may write to you and ask for your consent to check your relatives’ healthcare records to find the specific type of cancer they had. It may then turn out that your family history isn’t exactly what you thought it was. For example, if what you thought was an ovarian cancer was actually a cervical cancer. This may mean that there’s no clear pattern of inherited cancers in your family.
In cases like this, the family cancer or genetics clinic may decide that you don’t need to be seen. The regional genetics centre or your GP should tell you if this decision has been made. However, sometimes this doesn’t happen. So, if after a few months you haven’t heard from your GP or the regional genetics centre about your referral, it’s worth checking with your GP.
If the genetic specialists decide that you don’t need to see them, their letter to you should include a phone number you can call to discuss the reasons for this decision. If you have any questions about how they reached their decision, and what this means for your cancer risk, feel free to call them and speak to a genetic specialist over the phone.
In summary, having looked at your referral and your family history, a genetic counsellor or consultant may suggest one of the following actions:
not to do anything
to talk to other relatives
to have screening
to have a genetic test.