Genetic testing looks for specific inherited changes (variants) in a person’s genes. Genetic variants can have harmful, beneficial, neutral (no effect), or unknown or uncertain effects on the risk of developing diseases.
Harmful variants in some genes are known to be associated with an increased risk of developing cancer. These inherited variants are thought to contribute to about 5% to 10% of all cancers.
Cancer can sometimes appear to “run in families” even if it is not caused by an inherited variant. For example, a shared environment or lifestyle, such as tobacco use, can cause similar cancers to develop among family members. However, certain patterns that are seen in members of a family, such as the types of cancer that develop, other non-cancer conditions that are seen, and the ages at which cancer typically develops, may suggest the presence of an inherited susceptibility to cancer.
Genes involved in many of the known inherited cancer susceptibility syndromes have been identified. Testing whether someone carries a harmful variant in one of these genes can confirm whether a condition is, indeed, the result of an inherited syndrome.
Genetic testing is also done to determine whether family members who have not (yet) developed a cancer have inherited the same variant as a family member who is known to carry a harmful (cancer susceptibility predisposing) variant.
A different type of genetic testing, called tumor DNA sequencing, is sometimes done to determine if cancer cells of people who have already had a cancer diagnosis have genetic changes that can be used to guide treatment. Although some of these cancer cell changes may be inherited, most occur randomly during a person’s lifetime.
Most cancer syndromes are caused by harmful variants that are inherited in an autosomal dominant fashion; a single altered copy of the gene inherited from one parent is enough to increase a person’s chance of developing cancer. For most of these syndromes, genetic tests for harmful variants are available.
The features of a person’s personal or family medical history that, particularly in combination, may suggest a hereditary cancer syndrome include among others:
- Cancer was diagnosed at an unusually young age
- Several different types of cancer occurred in the same person
- Cancer in both organs in a set of paired organs (both kidneys or both breasts)
- Several first-degree relatives (the parents, siblings, or children of an individual) have the same type of cancer (for example, a mother, daughter, and sisters with breast cancer); family members with breast or ovarian cancer, colon cancer or endometrial cancer
- Being a member of a racial or ethnic group that is known to have an increased risk of having a certain inherited cancer susceptibility syndrome and having one or more of the above features as well
- Several family members with cancer
Genetic testing is often more informative if it can begin in a family member with a previous or current cancer diagnosis than in someone who has never had cancer.
Article submitted by the HPA Health Group
