Why cascade testing, a type of genetic testing, is key to cancer care

As families come together to celebrate the holiday season, the shared time can be an opportunity to talk about health. Although genetics may not be the liveliest of holiday dinner topics, family gatherings represent a unique opportunity to raise awareness about the important role that genetics can play in familial cancer risk, reduction and diagnosis.

cascade testing

At Seattle Cancer Care Alliance (SCCA), genetic testing is a vital part of cancer care. Genetic information can influence and guide cancer treatment—especially a type of genetic testing called “cascade testing,” which helps identify people at risk for a hereditary condition. SCCA genetic counselor Lorraine Naylor joins us to discuss Cascade testing, sometimes known as “cascade screening,” which refers to the process of testing biological relatives of an individual who has tested positive for a hereditary cancer syndrome to see if they too are positive.  

 

Q: Can you tell us more about cascade testing?  

A: Cascade testing occurs when a family member has already tested positive for a genetic mutation that increases cancer risk. Usually, the first person testing in a family has had a cancer diagnosis. Once we identify the genetic cause for that cancer diagnosis, we know exactly what to look for in other family members. Cascade testing is very clear-cut as far as results go because we know exactly what we are looking for. The results truly are a yes or no answer. 

Q: Which family members should be tested? 

A: Any family members of anyone who has tested positive for a hereditary cancer mutation or syndrome. Children, parents, cousins – anyone.  

Q: There are special considerations regarding children and genetic testing. At what age and in what situations should kids be tested?  

A: In most cases, we don’t test minors. There are a few exceptions for two or three genes that carry a risk of childhood cancer. In that case, it becomes a personal decision for parents. In most situations, we offer genetic testing to anyone over the age of 18.  

Keep in mind that the majority of screening recommendations don’t necessarily start until ages 20 to 25 at the earliest. Some gene mutations don’t change a person’s screening recommendations until age 30 to 40. For example, recommendations for women with BRCA1 and BRCA2 mutations are to start having breast MRIs at 25 and to add in mammograms at age 30. Recommendations for people with Lynch syndrome are to start colonoscopies between 20 and 25 years old. These are the two earliest-onset recommendations for the most common hereditary cancer syndromes that we see. 

So if you wouldn’t change anything or do anything differently until you’re 25, you may not want to test until you’re 25.  

Q: Is cascade testing new? Or are we just hearing more about it? 

A: Cascade testing has been around for as long as we’ve been doing genetic testing. Fifteen or 20 years ago, genetic testing in general was more abstract; now it’s becoming a standard of care so more people are getting genetic testing and more people are learning they are at risk, which results in more people getting cascade testing. 

Q: Where can you access cascade testing? 

A: It can be done by most labs, but if you want to make sure it’s done appropriately, I recommend going to a genetics provider. We run into lots of people who had genetic testing ordered by other providers and it ends up not being the right test. It can cost a lot more if a comprehensive test is incorrectly ordered instead of a specific test needed for cascade testing. 

Q: Is cascade testing covered by insurance? 

A: Almost always. Cascade testing is very rarely not covered by insurance. People think cost is a barrier but some labs offer discounted or even free cascade testing. 

Q: If someone is on the fence, why would you advise them to pursue cascade testing? 

A: Cascade testing shows us more accurately what cancers someone is at risk for. Learning what you are at increased risk for helps us to change screening recommendations to find cancers as early as possible, or in some cases even prevent it.   

Q: Are there arguments against doing this kind of testing? 

A: Some people don’t want to know that information. If they learn their mom has a BRCA mutation, they may not be ready to get tested themselves and potentially deal with the knowledge that they are at increased risk. As genetic counselors, we point out that having information gives you more options, but we also make sure and discuss all of the pros and cons of genetic testing, so each individual can make the decision that is best for them 

To learn more about cascade testing at SCCA, visit https://www.seattlecca.org/prevention/genetic-counseling-clinical-genetics

Gene The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein. Genetic counselor A health care professional with special training in medical genetics and counseling. Genetic counselors help patients and families who have, or who may be at risk of, a genetic condition. A health professional who has special training in medical genetics and counseling. Genetic counselors help patients and families who have, or who may be at risk of, a genetic condition. They help patients find out their chances of having a genetic condition or of having a child or other family member with a genetic condition. They also help patients understand their options for genetic testing, including its risks and benefits. After genetic testing is done, genetic counselors help patients understand their test results, including how the results can affect other family members. They also provide counseling and support. Genetic testing Tests that can be done to see if a person has certain gene changes known to increase cancer risk. Hereditary In medicine, this describes the passing of genetic information from parent to child through the genes in sperm and egg cells. Also called inherited. Lynch syndrome An inherited disorder in which affected individuals have a higher-than-normal chance of developing colorectal cancer and certain other types of cancer, often before the age of 50. Mammogram An X-ray of the breast. An X-ray of the breast. A mammogram is a method of finding breast cancer that can’t be felt using the fingers. Mammograms are done with a special type of x-ray machine used only for this purpose. Magnetic resonance imaging A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body. A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. MRI makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or X-ray. MRI is especially useful for imaging the brain, the spine, the soft tissue of joints and the inside of bones. Mutation Any change in the DNA sequence of a cell. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Any change in the DNA sequence of a cell. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Mutations can be harmful, beneficial or have no effect. If they occur in cells that make eggs or sperm, they can be inherited; mutations that occur in other types of cells are not inherited. Certain mutations may lead to cancer or other diseases. A mutation is sometimes called a variant. Screening Checking for disease when there are no symptoms. Because screening may find diseases at an early stage, there may be a better chance of curing the disease Checking for disease when there are no symptoms. Because screening may find diseases at an early stage, there may be a better chance of curing the disease. Examples of cancer screening tests are the mammogram (for breast cancer), colonoscopy (for colon cancer) and Pap and HPV tests (for cervical cancer). Screening can also include a genetic test to check for a person’s risk of developing an inherited disease.
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