The information below is intended for general education; a qualified healthcare provider may discuss your situation in more detail or specifics, which may differ from the information below.​
Somatic Cancer Testing
Somatic (meaning related to the cells) cancer testing is when genetic testing is done on the DNA from cancer cells. This testing may help your healthcare team understand if there’s a change in the DNA that is causing or contributing to the cancer. By finding a DNA change, we might get important information about diagnosis (the type of cancer), prognosis (what we might expect in the long-term), and treatment options that are best suited for you based on the genetic findings. For more information about this, we suggest discussing this with your healthcare team or oncologist.
Hereditary Cancer Testing
Germline (meaning in the cells you are born with) cancer testing is when genetic testing is done on a blood sample for a hereditary (passed down in the family) cancer syndrome. This is more often referred to as hereditary cancer testing. This testing is offered to patients with a particular history of cancer, a strong family history of cancer, if there is a known variant (or DNA change) in the family, or if a genetics expert finds other clues that are suggestive of a hereditary cancer syndrome. By doing this testing, we might get information about your chance to develop cancer and you can discuss next steps to ensure the best approach for your health. For more information about this you can continue reading below.
What is a hereditary cancer syndrome?
A hereditary cancer syndrome is when an individual is born with a DNA variant that makes it more likely to have cancer in their lifetime compared to the general population. Having a DNA variant does not mean that the person will absolutely get cancer in their life, but it means that they have a higher chance than someone who does not have a DNA variant.
For example:
Many people have heard of the BRCA genes – if a woman is found to have a DNA variant in BRCA1 or BRCA2, their chance of developing breast cancer can be greater than 60%, compared to woman who do not carry any DNA variants whose chance of breast cancer in their lifetime is around 12%. The woman with the BRCA variant is not destined to get breast cancer, but it is more likely for them than a woman who does not have the variant.
Why do some DNA variants increase the chance of cancer and cause a hereditary cancer syndrome?
Our bodies have thousands of genes coded into our DNA. We have two copies of each gene and these genes have jobs that help our bodies to function properly. If there is a mistake in the DNA of a gene, the gene may not work the way it is supposed to, which causes health issues. If one copy of a gene that is supposed to control how cells divide, repair mistakes in our DNA, or prevent tumour, stops working, then it is easier for cancer to develop. The body still has some ability to normally prevent cancer, but there is lowered protection because 1 of the 2 genes are not working the way it should.
What do I need to know about hereditary cancer syndromes?
They are rare – an estimated 1/10 cancer cases can be linked to a hereditary cancer syndrome. If a first degree relative (parent, sibling, child) has a DNA variant that leads to a hereditary cancer syndrome, then the chance to have the same variant is 50%. This is because you share half of your genes with your first degree relatives. Our knowledge is still evolving because there is still much to be discovered about genetics.
Who should have testing for a hereditary cancer syndrome?
How does genetic testing work?
At our laboratory, we use a blood sample to look at genes that are known to be associated with hereditary cancer syndromes to see if there are any changes to the DNA code (also known as variants) that lead to the gene not working.
Why is genetic testing for a hereditary cancer syndrome important?
Information from genetic testing might help: -Explain why someone got cancer -With decisions for cancer care or treatment steps -Inform risk of getting cancer, or other types of cancer -Take next steps for cancer screening and risk reduction, for example, someone may consider a risk-reducing prophylactic mastectomy (breast removal) -Family members better understand their risk so that they can make informed decisions for their health
How do I get testing for a hereditary cancer syndrome?
In Ontario, genetic testing for hereditary cancer syndromes is covered by OHIP if you meet certain criteria. This testing can only be ordered by a genetics professional, like a genetic counsellor, geneticist, or a specially trained oncologists and surgeons (in some cases).​ If you’re looking to direct your healthcare provider to information about genetic testing criteria, they can review the Ontario Health recommendations and see if you qualify for a referral to a Cancer Genetics Clinic. If you live in the Greater Hamilton Area, you may be referred to the Cancer Genetics Clinic at Juravinski Hospital. If you’re not in the Greater Hamilton Area, then a clinic in your area can found on the Canadian Association of Genetic Counsellors’ website. This testing cannot currently be requested by non-genetics professionals, like a family doctor.
Why can’t my family doctor order my testing?
Unlike other most other medical tests, genetic testing can have a broader effect on family members and there is important information that patients should understand before and after testing.
Prior to genetic testing, you should meet with a genetics provider who can clearly explain:
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Why testing is being offered to you
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What testing might find
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What this information would mean for you and your family
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The benefits of testing
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The limitations of testing
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There should also be opportunity for you to ask any questions you may have and have a discussion about if genetic testing is right for you. Not everyone wants to have this testing; some patients chose not to do genetic testing, or they chose to wait until another time.
For further questions and resources:
If you've had genetic testing for a hereditary cancer syndrome and have questions, we suggest contacting the provider who ordered the genetic testing.
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For reliable resources for families with a hereditary cancer syndrome, please visit:
