This content was provided by Anna Villa, MS, LCGC, genetic counselor, Parkview Cancer Institute.
What is genetic testing?
To begin this topic, we have to first understand what genetic testing is. In the cells of our bodies, we have inherited material called DNA. DNA is often described as an instruction manual for our bodies. It contains a code that our body reads through to know how to grow, develop and function.
Genes are sections of our DNA that tell our body how to do something very specific. I often describe genes as a specific recipe within a larger cookbook. Humans have around 20,000 genes. Only a very small fraction of those 20,000 genes are known to control cancer risk. So, when we talk about genetic testing for hereditary cancer syndromes, we’re really talking about testing somewhere between 30-50 genes.
When we’re testing those 30-50 genes, we aren’t looking to see if someone has those genes. We all have those genes and we have two copies of each one; one copy from our mother, and one from our father. The job of those genes is to protect us from developing cancer. Genetic testing looks to see if those genes are written correctly or if there is a mutation disrupting that gene’s ability to protect us the way it should. If the gene is written correctly, it makes a healthy protein that is then the structure that provides cancer protection. If the gene has a mutation, it makes a damaged protein that either doesn’t protect us at all, or does not protect us as well.
Cancer causes
All cancer is genetic but most cancer is not inherited. All cancers occur due to mutations in genes, however, there is an important distinction between mutations in genes that are acquired (mutations that develop in a few cells over our lifetimes) and those that are inherited (present in the egg or sperm that formed us and therefore, present in every cell in our bodies).
Cancer can be hereditary, familial or sporadic, and the breakdown looks like this:
- 5-10% hereditary
- 15-25% familial
- 65% sporadic
Sporadic cancers are caused by acquired mutations, and account for the majority of cancers. Hereditary cancers are caused by inherited mutations and account for only about 10% of cancers. Familial cancers appear to have an inherited component, but not one that is easily identifiable.
The first step in identifying individuals who are at a higher risk for cancer, is to consider which of these categories a particular person/family seems to fall into. Genetic counselors can help you figure this out by taking a thorough family history. Once we learn more about your family, we can assess whether the pattern of cancer we see seems to be familial, hereditary or sporadic. Based on that information, we can recommend genetic testing, recommend altered screening plans or provide reassurance that the cancer in your family is unlikely to have a hereditary cause.
Tying the cause to improved outcomes
Understanding how the cancer originated leads to more personalized risk management. We know that:
Sporadic = average risk for other cancers
Familial = increased risk for the cancers seen in close family members
Hereditary = increased/high cancer risk across multiple cancer types
If the patient does test positive for hereditary risk factors, there are a handful of options to consider, including:
- Avoidance of risk factors
- Increased surveillance
- Risk-reducing agents
- Risk-reducing surgery
The higher your risk, the more we should do.
I have breast cancer. Should I have genetic testing?
We recommend genetic testing if a patient meets any of the following criteria:
- breast cancer diagnosed at or before age 45
- breast cancers in close relatives, if one of those family members was diagnosed at or before age 50
- breast cancers in close relatives (same side of family) diagnosed at any age
The National Comprehensive Cancer Network, an alliance of 28 leading cancer centers devoted to patient care, research and education, has guidelines/criteria for who is most likely to carry a gene mutation and therefore, should be tested. These guidelines are based on a combination of data and expert opinion.
The guidelines are complex, but the main idea is this: The older someone is at the time of diagnosis, the more family history they need to meet the criteria for testing. The younger they are at the time of their diagnosis, the less family history they need.
We also recommend for rare cases, including male or triple-negative breast cancer diagnosed at or before 60 years of age. It’s important to acknowledge that these guidelines change over time and the recent trend is that they are becoming broader and more inclusive, so more and more people are meeting the criteria for testing.
I recommend genetic testing if you value it and if you feel that the benefits outweigh potential risks.
I already have breast cancer. Can’t I just tell my sisters/daughters to get genetic testing?
Once it has been established that a family history is suggestive of hereditary breast cancer, it’s important to identify the best family member to test. Genetic testing is always most informative when testing someone with a personal history of cancer because we need to be able to identify the cause of someone’s cancer before we can tell their family members much about their own risks.
I had genetic testing years ago. Do I need it again?
It really depends on when the testing was done. If an individual was tested prior to 2013, there is likely updated testing that involves analysis of more genes.
Common concerns
Cost
Most people who meet NCCN guidelines will also likely_ meet coverage criteria with their insurance. The majority of labs will call you regarding out-of-pocket expense, but overall, the cost of genetic testing has decreased over the past few years.
Discrimination
A lot of people have concerns about insurance discrimination based on genetic testing results.
There is a federal law (GINA) that protects most people from employment and health insurance discrimination.
The important thing to remember is that genetic testing results can significantly change medical management and inform patients about risk-reducing surgeries or increased screenings at younger ages. This testing is ever-changing, so it’s important to communicate with your care provider. Genetic testing might not be for everyone, but your doctors and genetic counselors are here to help you make that decision!
