Cancer Genetics: How Cancer Sometimes Runs in the Family

If you're worried about cancer in your family

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 or specialist. 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.

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 occured 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

Your GP may ask you questions to assess your risk of cancer. This is based on your family history of cancer. If your GP thinks cancer may run in your family, they will refer you to a genetics specialist. This could be in a family cancer clinic or a cancer genetics clinic.

Further reading:

Cancer Genetics - an information booklet produced by Macmillan Cancer Support

Below is a video to help understand family history and cancer genetics. Genetic Counsellor Matilda Bradford explains the role of the Clinical Genetics service, and how it can support families affected by cancer.

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