Cancer risk and family history

Everyone lives with some risk of getting cancer. Often, there won’t be a clear cause, but there may be risk factors. These are often related to lifestyle, such as whether you smoke or are overweight. Getting older is the biggest risk factor for most people.

People are sometimes concerned that their family history of cancer means they are at higher risk. Some cancers, including breast, ovarian, bowel and womb, can have a genetic link. But only a small proportion of cancers are associated with a family history. And even if you do have an increased risk because of this, it doesn’t mean you will definitely get cancer.

If you are concerned about your risk of cancer, or your family history, talk to your GP.

What is the risk of getting cancer?

Most of the time, we don’t know exactly what causes any particular cancer, but we do know some of the risk factors for cancer. Having a particular risk factor doesn’t mean that you will definitely get cancer.

Some risk factors are very likely to cause cancer, whereas others will only slightly increase the risk of getting it. Usually cancer is the result of a combination of several risk factors.

Having a particular risk factor for cancer doesn’t mean that you will definitely get cancer – just as not having it doesn’t mean that you won’t.

Smoking is a good example of this. If you smoke, it isn’t certain that you will get lung cancer – just as if you don’t smoke, it’s not certain that you won’t. But smoking will greatly increase your risk of getting lung cancer. About 9 out of 10 people who develop lung cancer are smokers.

For most people, increasing age is the biggest risk factor for developing cancer. In general, older people (those over 65) are far more likely to develop cancer than younger people (those under 50).

Cancer is very common. Most of us have relatives who have had cancer. Some people worry that a history of cancer in their family greatly increases their risk of developing it. But, in fact, fewer than 1 in 10 cases (5–10%) are associated with a strong family history of cancer.

Assessing your personal risk of cancer

Assessing your personal risk of cancer is complex. Having a higher risk means you are more likely to get cancer than people in the general population. But, even if you have a cancer susceptibility gene, this doesn’t mean that you will definitely get cancer. Certain questions help to assess your cancer risk:

How many of your relatives have been diagnosed with cancer?

  • What age were they when they were diagnosed?
  • How many relatives have not had cancer?
  • Have there been any rare cancers or combinations of cancers in your family?
  • Have there been certain combinations of cancers in your family, such as bowel and womb cancer, cancer in both breasts, breast and ovarian cancer or breast cancer in a male relative?
  • How old are you?

Everybody lives with some risk of developing cancer. Even if you aren’t at increased risk, you still have the same chance of getting cancer as the general population. Most people who get it don’t have one of the known cancer susceptibility genes.

Assessing your risk of cancer may help you and your doctor to decide what level of prevention and screening is sensible for you. For example, if you are at significantly increased risk of bowel cancer, you’ll be offered regular tests to check your bowel for pre-cancerous changes (bowel screening).

If you think you may be at increased risk of cancer, because of your family history, you can talk to your GP. If your GP agrees with you, they can refer you to a specialist, cancer genetics service.

There are tests for alterations in genes that increase the risk of getting breast, ovarian and bowel cancer, as well as for some rarer cancers. Genetic testing is normally only possible if you have a relative with one of these cancers who is willing to be tested first.

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 womb (endometrial) cancer, sometimes with other cancers such as stomach, kidney, ovarian, ureter or renal pelvis cancer.

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.

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.

Back to Family history

Cancer and genes

Changes (mutations) in some genes can cause cells to grow in an uncontrolled way, forming tumours.

Genes and how they work

Genes are passed down to us from our biological parents. They affect how our bodies look, grow and work.