Most cancers are caused by multiple factors that occur over the course of a lifetime. These factors can include age, lifestyle, environment, chance, and family history.
Some cancers are called hereditary, meaning that they are caused by a
pathogenic variant that is passed down from parent to child.
Genetic testing can be used to find out if your cancer or the cancer in your family has a hereditary cause. Hereditary cancers happen because of a pathogenic variant in a gene that normally protects against cancer. Hereditary cancer is not common. About 5 to 10 out of 100 people with cancer have a pathogenic variant in a hereditary cancer gene.
If you have already had cancer, hereditary cancer testing might tell you why you got cancer. If you are still being treated for cancer, it might be used to make treatment decisions.
Hereditary cancer testing might also tell you if you have a high chance of getting other types of cancer and if there are ways to lower your chance of getting cancer or finding it early.
Deciding who to test
In Alberta, genetic testing is covered by the Alberta Health Care Insurance Plan if your medical history or if your medical and family history shows possible signs of hereditary cancer. Genetic counsellors and healthcare providers look at many factors to determine who is eligible for genetic testing. These factors include:
- the type or types of cancer
- the age that you or your family members were diagnosed with cancer
- your family history of cancer
Possible signs of hereditary cancer include:
- being younger than average when you (or your family member) are diagnosed with cancer
- having a rare cancer or cancers
- being diagnosed with more than one type of cancer
- having multiple family members with the same or related cancers on the same side of the family
Genetic testing usually starts with a family member who has had cancer. If a pathogenic variant is found, then other family members can have genetic testing to find out if they're also at high risk of developing cancer.
Results
Hereditary cancer testing is most commonly done on a blood sample. It can give 3 kinds of results:
- Positive: A pathogenic variant was found in 1 or more of the genes tested. When a pathogenic variant is found, you may be told that you have a hereditary cancer condition. A positive result might:
- explain why you had cancer
- help guide your cancer treatment
- tell if you have a higher risk to develop new cancer or cancers
- provide helpful information and the option of genetic testing for your family members
- lead to screening or prevention measures to protect you from developing another cancer or to catch cancer early if it does develop
- Negative: No pathogenic variants were found in the genes tested. This significantly decreases the chance that you have a hereditary cancer condition. But other factors like your personal and family history can also determine your future cancer risks. Your genetics healthcare team can tell you what a negative result means for you and your family members.
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Uncertain: A variant was found, but that variant is not well understood at this time. The variant of uncertain significance may be a pathogenic variant that increases the risk for cancer or it might be a harmless genetic variant that does not increase the risk for cancer. Your genetics healthcare team will tell you what this result could mean based on the specific variant, your personal history of cancer, and your family history of cancer.
Tumour screening
If you have had a biopsy test (where a small sample of tissue is removed from your body), your healthcare team might do
pathology tests to learn more about the cancer.
These pathology tests can sometimes show that you have a higher-than-average chance to have a hereditary cancer condition.
Learn more about a
positive screen for Lynch syndrome and tumour genetic testing.
