It is not entirely clear whether a family’s pattern of cancer is due to chance, similarities in the lifestyle choices of family members or hereditary factors passed from parents to children through genes.
People from the same family share many characteristics. For example, parents pass on physical traits to their children like eye colour, hair colour and body shape. Also, brothers and sisters may have similar personalities, and they may be good at the same kinds of activities. Our parents pass characteristics on to us through units of information called genes.
Our bodies are made up of cells. Genes are present in every cell and guide how each cell develops and functions. Over the past few years, scientists have learned a great deal about how changes in our genes (gene mutations) can influence our health.
Gene mutations can occur in 2 ways. They can be inherited from a parent or they can be the result of changes that occur during a person’s lifetime. Every cell has the ability to spot these changes and fix them before they are passed on to new cells through the normal process of cell development. Sometimes a cell’s ability to make these repairs fails and the altered gene may be passed on. Certain gene mutations that are passed on may increase the risk of developing cancer.
While all cancers could be considered to be genetic – as they are triggered by altered genes – only a small portion of cancers (up to 10%) are passed on from 1 family generation to another. The risk of having an inherited gene mutation is generally talked about in relation to 1 of 3 groups – low, medium or high. A cancer might be considered hereditary for a family if:
- the cancer is present in a number of generations
- family members have developed cancer when they were younger than 50 years of age or at a younger age than usual for that type of cancer
- family members have had more than 1 type of cancer
Depending on your risk of developing cancer, cancer specialists may advise certain preventive and/or early detection measures. These recommendations may be made with or without genetic testing.