Genetic testing can usually be done by using a blood or saliva sample. If someone has had a bone marrow transplant, or has an active hematologic malignancy (leukemia, lymphoma), occasionally a skin biopsy must be performed instead.
The purpose of genetic testing is to look for changes in genetic material or genes that are related to cancer risk. Genetic testing involves analyzing or reading a gene to identify mutations that are associated with an increased risk for cancer. However, genetic testing will not tell you if you currently have cancer or if you will develop it for certain in the future.
Positive Genetic Test Result
A positive genetic test result means that you may be at higher risk to develop certain cancers depending on the gene involved. Knowledge of these risks can help your health care provider offer the best cancer screening options, as well as possibly risk-reducing surgeries or medications. The mutation may also impact family members, such as children, siblings, parents, aunts/uncles, cousins, and grandparents. Typically, these gene mutations are inherited from a parent, so it is likely that others in the family are at risk and may not yet know it. Genetic testing could be offered to family members to help them understand their cancer risks.
Negative Genetic Test Result
A person’s risk for cancer does not go down to zero percent, even with negative genetic testing. Genetics is a field that is still growing, and we do not know about every gene associated with hereditary cancer at this time. Having negative genetic testing means that we do not know what is causing the cancers in the family. These cancers could be due to a gene that we cannot yet test for, or could be due to shared environment. Even with a negative genetic test, there could be a higher risk for relatives to develop cancers observed in the family. Talk to a genetic counselor to see what your risks might be and what is recommended for you.
Even if you had a negative genetic test, there could still be a genetic reason for cancer risk in the family as a whole even if you, as an individual, do not carry that gene or genetic mutation. For this reason, another person in your family may be recommended for genetic testing even if your test was negative/normal. We call this person the ‘best test’ in the family – a relative with the highest chance to have a hereditary cancer risk factor. This could be a relative who was diagnosed with a certain cancer at the youngest age or a relative who has certain factors in his or her medical history that raises their risk of having a genetic reason for their cancer. If that relative has a positive test result, it would then affect risk for other family members. If your genetic counselor says that someone else in your family is still a good candidate for genetic testing, he or she may be able to give you a letter that briefly describes this for you to send to the relative. Talk to your genetic counselor to discuss details of your particular family history.
While there have been great advances with the technology used for genetic testing, some genetic mutations may still be missed. Updated genetic testing may be available as the technology continues to improve, and it is important to keep in touch with your genetic counselor.
Uncertain (Variant of Uncertain Significance) Genetic Test Result
Everyone has variations in their genetic information that makes him/her unique, and most of the time these are benign and do not cause health issues. An uncertain result means that a change, also known as a "variant of uncertain significance," was identified with testing. However, we currently do not have enough data about the specific variant to determine if it is a benign change, or one that could be associated with cancer.
Uncertain results are not used to make any decisions regarding your care. These uncertain variants sometimes get reclassified once we are able to learn more about the particular variant(s), at which point there may be an impact on your management.
Talk to a genetic counselor to see what your risks might be and what is recommended for you.
Updated Genetic Testing or ‘Panel’ Testing
Starting in 2013, newer technology became available to test many genes at one time with one blood sample. Some people call this “panel” testing since it allows us to look at a panel of genes, but technically it’s called “next generation sequencing.” This allows potential cost-savings and decreased time to get all results since we do not have to order separate tests for every gene we want to analyze. It also gives us the opportunity to test for more rare genes that insurance would seldom cover in the past (and hence, never have testing completed).
For example, in hereditary breast cancer, the BRCA1/BRCA2 genes are the most common genes involved; however, we now know there are at least 15 other genes that have impact on breast cancer risk in rare families. We can examine these in one test through the newer testing technology. The “panel” testing can include the BRCA1/2 genes to ensure these are updated if a person has had some of those genes tested previously.
It’s important to remember that this is not like other blood tests. There are also risks and limitations to this type of testing, as with any genetic testing, including unexpected or uninformative results (such as variants of uncertain significance), difficulty with result interpretation, potential issues with insurance coverage, and others. We recommend a detailed conversation about this technology and the issues surrounding it with your genetic counselor.