Cancer risk and family history

Everyone has 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 smoking or being overweight. Getting older is the biggest risk factor for most people.

People are sometimes worried that their family history of cancer means they are at higher risk. But only a small number of cancers are associated with a family history.

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

Your GP or a genetics specialist may assess your risk of getting certain cancers. You will be asked questions about your family history of cancer.

Based on your answers, they may assess your risk of getting a certain cancer as:

  • average risk (population risk)
  • moderate risk (raised risk)
  • high risk.

What is the risk of getting cancer?

More than 1 in 3 people in the UK will get cancer during their lives. Everyone has a certain risk of developing cancer. A combination of genes, lifestyle and environment can affect this risk.

Most of the time we don’t know exactly what causes a particular cancer. But we do know some of the risk factors for that cancer. Risk factors are things that can make you more likely to develop cancer. They include being older, smoking and being overweight.

Having a particular risk factor doesn’t mean you will definitely get cancer. Some risk factors only slightly increase the risk of developing cancer.

Usually, cancer is due to a combination of several risk factors. But some risk factors are more likely to cause cancer than others. Smoking is a good example of this. Smoking will greatly increase your risk of getting lung cancer. About 9 out of 10 people who develop lung cancer are smokers. But not everyone who smokes will develop lung cancer.

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

Cancer is very common and most of us have relatives who have had cancer. People often worry that a history of cancer in their family greatly increases their risk of developing it. But fewer than 1 in 10 cancers are associated with a strong family history of cancer.


When cancer may be linked to an inherited gene

Most cancers aren’t caused by inherited cancer genes. If only one or two older relatives have had cancer, your family is not likely to have a cancer gene.

If you think cancer might run in your family, talk to your GP. They will ask you about any close blood relatives who have had cancer. People you are related to by marriage are not blood relatives. Close relatives are parents, brothers, sisters, sons, daughters, aunts, uncles and grandparents.


Assessing your risk of cancer

This means estimating your risk of getting certain cancers that may run in your family.

This happens at the genetics clinic when you meet the genetics specialist. Your GP may also do this when deciding whether to refer you to a genetics clinic.

You will be asked:

  • how many of your relatives have had cancer
  • what age they were when they got cancer
  • how many relatives have not had cancer
  • whether there have been any rare cancers in your family
  • whether there have been certain combinations of cancers in your family – for example breast and ovarian cancer or bowel and womb cancer
  • your age.

Based on this information they may assess your risk of getting a certain cancer as one of the following:

  • Average risk (population risk) – Your risk is the same as, or close to, that of people without a family history of the cancer. You’re more likely not to get the cancer than to get it.
  • Moderate risk (raised risk) – Your risk is higher than average. But it’s not likely there is an inherited cancer gene in the family. You are more likely not to get the cancer than to get it.
  • High risk – You have a high risk of developing the cancer in your lifetime. But it doesn’t mean you’ll definitely get it. There may be an inherited cancer gene in your family.

Knowing your cancer risk can help you decide what to do to reduce it. This might include treatments to prevent cancer and screening to find it early.


When cancer may run in a family

It’s possible your family may have an inherited cancer gene if:

  • two or more close blood relatives on the same side of the family had the same type of cancer
  • members of your family have had cancer at a young age (under 50)
  • certain cancers have occurred on the same side of the family
  • a close relative has had more than one primary cancer, which means that they have had cancer twice, but the second cancer was a new cancer and not the first cancer spreading to another part of the body
  • you have a family history of cancer and have Polish, or Ashkenazi Jewish (Eastern European Jewish) ancestry – certain inherited cancer genes are more common than in the general population.

Back to Family history

Cancer and genes

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