What is Genetic Testing?
- Genetic testing for breast cancer is an "exploding" area, experts say. And this testing method is only going to become more common practice.
- This type of testing is done to determine if a person has a specific mutation that puts them at a higher risk of developing cancer.
- Like anything in life, there are limitations to genetic testing for breast cancer, specifically the commercially available tests women can take. And one of those limitations is the lack of genetic counseling available to people who receive positive results on a genetic test.
"It started out with a very narrow field of women and men who were recommended to have it based on certain risk factors, family history of breast cancer, or other cancers, and also ethnic backgrounds," Dr. Elisa Port, a surgical oncologist at Mount Sinai, tells SurvivorNet during a recent interview.
Read MoreWhat is Genetic Testing?
This type of testing is done to determine if a person has a specific mutation that puts them at a higher risk of developing cancer. Genetic testing can be done on samples of blood or saliva, or from a swab of the inside of a cheek, according to the American Cancer Society. The samples are sent to a lab for testing.Genetic testing for cancer is usually done in a doctor's office (either your primary care doctor or an OB-GYN), but there are a few tests available for people to purchase commercially.
Where Can I Get Genetic Testing?
What Are the Types of Gene Mutations?
Before taking a genetic test to see if you have a higher risk of developing breast cancer, it's important to be educated on the different types of gene mutations that increase your risk of this cancer.
The most common breast cancer gene mutation, and the one doctors have known about the longest, is the BRCA gene mutation. The BRCA1 (BReast CAncer 1) or BRCA2 (BReast CAncer 2) genes help cells repair their DNA damage. Having a change, or mutation, in one of these genes increases a woman's risk of getting breast cancer. These gene mutations are commonly passed down in families; if a parent carries a BRCA gene mutation, there's a 50-50 chance you could be carrying it as well.
Between 5% and 10% of breast cancer cases are thought to be hereditary. And about 10% of patients who undergo genetic testing will test positive for the BRCA1 or BRCA2 gene, Dr. Julie Rani Nangia, an assistant professor at Baylor College of Medicine, tells SurvivorNet.
"The genetic BRCA1 and (BRCA)2 mutations, if a woman has one of these mutations … it puts her at basically the highest quantifiable risk for getting breast cancer," Dr. Port says. "We typically say between the 60 (percent) and 80 percent range. Having a BRCA1 and (BRCA)2 mutation also means that that person is at higher risk of getting breast cancer at an earlier age, and also maybe at risk for other cancers like ovarian cancer, like pancreatic cancer for men, prostate cancer and male breast cancer may be a concern."
Since the discovery of the BRCA mutations in the 1990s, doctors have gone on to identify many other gene mutations that put people at a higher risk of developing breast cancer.
"There's actually eight to 10 genes that also can put someone at a higher risk for breast cancer," Dr. Port says, adding that usually that risk isn't as high as the BRCA mutations. These additional gene mutations include PALB2, ATM, TP53, CHEK2, PTEN, CDH1 and STK11.
Should I Get Genetic Testing to Assess My Risk for Breast Cancer?
"We call them more moderate penetrance genes and those genes, the risk of breast cancer associated with them can be anywhere from say 20 percent to 50 percent. … so still very high, but lower than the BRCA genes that were the ones we originally described."
The PALB2 gene is a "moderate penetrance gene, and the risk of getting breast cancer with PALB2 can be a pretty broad range," Dr. Port says. "And unlike the BRCA genes where we don't really use the family history of who got breast cancer to affect the risk estimates, with PALB2, you really can dial up risk or dial down risk depending on how many relatives and the age of the relatives in the family got breast cancer."
Limitations of Genetic Testing
Like anything in life, there are limitations to genetic testing for breast cancer, specifically the commercially available tests women can take. One of the most common types of commercially available tests is from 23andMe, a genomics and biotechnology company, as well as tellmeGen and MyHeritage genetic tests.
"There's only a cadre of them that are approved and accurate and there can be both false positives and false negatives, so it really depends," Dr. Port says. "If someone is suspicious of having one of these genes (mutations) and gets tested through one of what we call the direct to consumer type tests, it is important that those testing results may need to be verified before doing something irreversible based on those results."
In other words, if you take one of these tests without your doctor's knowledge, and you receive some concerning results, make sure you discuss those results with your doctor before taking your next steps.
Genetic Counseling
The other limitation to genetic testing is genetic counseling. Dr. Port says this is the most critical part of genetic testing. What does genetic counseling mean? Well, if you get a positive result back, how are you going to cope with that news?
"If someone gets a genetic test result back, it's really important for them to know what is this? (What does this) mean for them? Put it into context."
"What does it mean for their family members? For their relatives? Genetic counseling to follow up genetic testing is a really, really important part of the whole process and is not always available in the direct to consumer type avenue."
Based on your personal and family health history, your doctor can refer you for genetic counseling, according to the U.S. Centers for Disease Control and Prevention.
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