What is Genetic Cancer Testing and How Do Patients Get Tested?


Dr. Barry Tong, a genetic counselor in the cancer genetics and prevention program at UCSF, discusses what genetic cancer testing is, the different types of testing, different results, and why going to a genetic counselor beforehand is so important.

At the molecular level all cancers are genetic, they start as your normal breast cell or ovaries and overtime pick up small genetic changes. When talking about inherited testing or hereditary testing only a small portion of cancer can be passed down in a family. “We roughly quote 5-10% can be due to hereditary reasons or something we might find in an inherited genetic test,” explained Dr. Tong at the CURE® Educated Patient® Women’s Cancer Summit.

“Genetic testing is a critical part of understanding these cancers, as well as how to treat, and I’ll be discussing today about how we think about how genetics fits in cancer development, how genetic testing plays a role and how genetic counseling can help induvial and families come to decisions around genetics,” says Dr. Tong.

Some exceptions include, up to 20% of negative breast cancers that can be hereditary and up to 25% of ovarian cancers can be hereditary, which is why genetic testing is recommended for all ovarian cancers.

When talking about hereditary cancer Dr. Tong says clinicians and genetic counselors are thinking about if that person has a higher chance of developing cancer, because nobody is at a 0% of developing cancer. Genetic testing will look at to see if they can identify what is elevating the person’s risk of developing cancer, and can you potentially explain why a person developed certain cancer.

“Part of what we learn from genetic testing, is not only could it have been due to a hereditary cause, such as a mutation in a gene, but which gene mutation and how can we differentially take care of people depending on which gene mutation did cause that,” says Dr. Tong.

Guidelines recommend that all women diagnosed with epithelial ovarian cancer and breast cancer should be offered genetic testing.

Beginning in 2015 technology has brought three different types of gene testing or as they call it, Multi-Gene Panel Testing. Then there is a decision about how much genetic testing to do. For genes that they know are associated with inherited risk, those are high and moderate risk genes, they have actionable guidelines for treatment, risk reduction or prevention.

As technology develops you think about if the low-risk genes should also be looked at, the most likely have no impact on your health, such as a recessively inherited cancer risk, the information from these genes may be relevant to your family members or future generations. Some panel offers looking at newly described genes, they have limited evidence that they may impact inherited cancer risk, and they don’t have actionable guidelines yet but could in the future.

“We think that pretest counseling with a genetic counselor can help an induvial better understand how genetics impacts or plays a role in their cancer diagnosis or in their family history. Genetic counselors will take a look at family history and go many generations to look at distant relatives to see if there is a pattern to the cancers of that family that can be inherited, or does it look more like sporadic risks, then that counselor can discuss what the testing options are, how much testing to have or if it’s even right for you or not,” says Dr. Tong about genetic testing counseling.

Types of results include a negative, the most important to be working with a genetic counselor, meaning there was no change found in the gene, it is considered a “normal” result and cancer treatment, screening and prevention decisions can be based on personal and family history of cancer. The next is a variant or uncertain significance, also considered a “normal” result, a change was found but is most likely due to normal human variation. The last result is positive result, where they find a change or genetic mutation that is associated with cancer, cancer treatment, screening and prevention decisions will be based on the risks specific to the change found.

Some may fear that they may be discriminated against due to their genetic testing results. There are laws in place that will protect you and your family members from employment or health insurance discrimination such as the Genetic Information Non-Discrimination Act of 2008, or GINA. In addition, there is the Americans with Disabilities Act, ADA, and the Health Information Portability and Accountability Act, HIPPA. However, there are limitations, how these laws don’t protect against other types of discrimination such as life insurance, disability or long-term care, which would be discussed in your genetic counseling session.

“Genetic testing can help thinking about what the path forward is for you and your family when we do learn the results,” Dr. Tong concludes. He says going to a genetic counselor can help medically keep you healthy and also emotionally, connecting you with different resources and support organizations.

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