After a cancer diagnosis, patients often have questions about what it could mean for their family members as well as their own treatment. Tim Hakim, MS, CGC, a certified genetic counselor at Northside, explains how genetic testing for hereditary cancer can guide care decisions and clarify inherited risk.
What is genetic testing for hereditary cancer?
About 10%-15% of people with cancer have an inherited predisposition for certain kinds of cancer. (This increases to about 20%-25% of people with either ovarian or metastatic prostate cancer.) A hereditary cancer predisposition means a mutation (broken copy) of a gene is inherited from either parent, which leads to higher cancer risks. Genetic testing can help determine whether someone has a hereditary cancer predisposition.
What are the benefits of genetic testing after a cancer diagnosis?
Genetic testing can help determine whether the patient or their family members may be at increased risk of other cancers in the future. It can also help clarify whether other family members may have inherited a cancer predisposition.
Testing the person with cancer is generally considered more informative than testing their children who have not had cancer. This is because if a child does not have a mutation identified in genetic testing, their parent may still have had a mutation that was not passed on to them but could have been passed on to their other children.
In addition, genetic testing can sometimes change the treatment of a patient’s current cancer. Genetic testing can also indicate that specific targeted therapies may be more useful for a particular patient.
What are the advantages of meeting with a genetic counselor before and after genetic testing?
Genetic counselors are health care providers with graduate training in genetics who can communicate complex medical information to patients. A genetic counselor will usually meet with a patient before testing to review their personal and family history of cancer. They can then determine whether genetic testing is recommended and explain possible genetic findings. By documenting the family’s cancer history, they can increase the likelihood that insurance will cover genetic testing when appropriate. A genetic counselor will explain the benefits and risks of genetic testing to help the patient make an informed decision.
After genetic testing results are available, a genetic counselor can explain any findings and medical management recommendations. They can also identify other family members who may benefit from genetic testing.
Which family members should be informed if a patient has a positive genetic testing result? What should they be told?
Ideally, at least living first-degree relatives — children, siblings and parents — should be informed of a positive genetic test result, as each has a 50% chance of carrying the same mutation. Beyond that, aunts, uncles, cousins, nieces and nephews may be appropriate to inform about a positive result. We encourage cascade testing, meaning results from one relative inform whom else to test. For example, if a sibling tests positive for the mutation, there is a chance it could be passed on to their children. But if the sibling tests negative, there is no concern about the mutation being passed on to their children. Often, who to inform also depends on family dynamics and whom someone feels comfortable informing. Northside genetic counselors provide patients with a family letter to give to relatives. The letter explains the gene in which a mutation was found and how family members can get tested.
What does it mean to receive an “uncertain result”?
About 40% of people will have a variant of uncertain significance, or VUS, found during genetic testing. A VUS is a variation in one of the genes tested for which the lab lacks sufficient information to classify as either harmful or benign. Individual variants are rare and hard to classify, but VUSs are a very common finding. Genetic counselors typically are not overly concerned about VUSs and do not recommend changing medical management based on them.
If the lab later reclassifies the VUS as more evidence is collected, a Northside genetic counselor will notify the patient. Most VUSs that are reclassified are moved to benign, indicating the lab is confident the variant does not affect cancer risk. Also, while an individual VUS may not have much known about it, the gene it is in usually contains crucial information. For example, the VUS may be in a gene associated with colon and uterine cancer, and there may be no personal or family history of these cancers. A genetic counselor can help explain the particulars of a patient’s VUS, including analyzing the variant in the context of the patient’s personal and family history.
Closing thoughts
Cancer takes a terrible toll. But when we can proactively identify people who are at higher risk due to an inherited mutation in a cancer predisposition gene, we can target appropriate medical management to prevent cancer or catch it at an earlier, easier-to-treat stage. Hereditary cancer genetic testing is one way to thwart cancer and improve outcomes for future generations.
For more information or to speak with a genetic counselor or Cancer Genetics Program staff member, call 404-851-6284 or email genetics@northside.com.
LEARN MORE ABOUT CANCER GENETICS AT NORTHSIDE.
