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Hereditary cancer is caused by a change in a gene (called a mutation or variant) which is passed down from generation to generation in a family. Family members who inherit the hereditary cancer gene mutation face a higher lifetime risk for certain types of cancer, depending on the gene involved. Families with a hereditary cancer condition (or syndrome) may have a clustering of certain types of cancer in closely related family members, and there may be relatives with more than one cancer during their lifetime.  In these families people often develop cancer at a younger age than usual. 

It is important to note, most cancer is not hereditary, but happens by chance and is influenced by age, environmental factors, and lifestyle choices.

No, not everyone with a hereditary cancer condition will develop cancer in their lifetime. For example, in a family that has “hereditary breast cancer”, there will likely be family members who live a long lifetime, and never develop any type of cancer.

People who have a mutation in a hereditary cancer gene have an increased risk to develop one or more types of cancer compared to other people who find out that they don’t have that mutation.   

The likelihood of being diagnosed with cancer depends on several factors, including,  the gene involved, the person’s biological sex, environmental factors, and whether the person has undergone risk-reducing management (example: a mastectomy or removal of the breast tissue to reduce risk for breast cancer).  

People who receive a positive genetic test result often have genetic counselling, so they can better understand their cancer risks and future cancer screening and medical management options.

Everyone will have their own personal reasons for wanting to find out whether they have a hereditary cancer condition. Genetic testing is used to confirm whether someone has a hereditary cancer condition or not.
 

Some common reasons for wanting genetic testing when it is offered after a cancer diagnosis include:

• It may help provide an explanation for why a person developed cancer.
• It may help a person’s oncologist determine what is the best treatment plan, and whether a person is eligible for a specific medication.
• It may provide more precise information about the chance of developing a second, and unrelated cancer during one’s lifetime.
• It may help a person decide about future cancer screening and prevention options. For example, risk reducing surgery to remove breast tissue for those known to have a high lifetime risk of breast cancer.
• It may help other family members understand their chance of developing cancer, as well as their options for screening and prevention.

Some of the common reasons to want genetic testing for those who have never had a cancer, but know of a hereditary cancer condition in their family, include:

• It may provide more information about lifetime cancer risks.
• It may help determine cancer screening and prevention options.
• It may help other family members understand their chance of developing a cancer and access screening or preventative options.

While there are many reasons people may want to know if they have a hereditary cancer condition, there are also reasons why people may not want to know this information.  There are also many valid reasons to delay genetic counselling and/or genetic testing to a later time in one’s life. Meeting with a genetic counsellor will allow you to explore which option is best for you at this time.

Yes. A mutation in a hereditary breast cancer gene can be inherited from either a person’s mother or father. It is a myth that risk for breast cancer cannot be passed down from the father’s side of the family.

This means it is important to review the family history of breast cancer on both sides of the family during a hereditary breast cancer risk assessment. 

Men can develop breast cancer, however, the risk for a man with a mutation in a hereditary breast cancer gene to develop breast cancer is significantly lower than a woman with a mutation in the same gene. 

If there is a known hereditary cancer condition in a family, and a person tests negative for the specific mutation seen in their relatives, it means they do not have the increased risk for cancer associated with having that gene mutation.  

However, no genetic test can eliminate the risk for a person to get cancer. This is because most of the time cancer occurs sporadically, influenced by risks related to a complex combination of increasing age, environmental factors, and lifestyle choices. A person who is negative for the hereditary cancer condition known in their family can still develop cancer sporadically, like other people in the general population. 

A person’s residual risk for cancer after genetic testing should be discussed with their healthcare provider, as there are multiple factors to consider.