Breast Cancer Genetics
Have you or a relative been diagnosed with breast cancer? Then, you may be curious about whether it runs in the family. That's particularly true if more than one family member has had breast cancer. Like many health conditions, there can be a genetic link, although this appears to be the case in only a small percentage of patients. It's somewhere around 5 to 10%. When it runs in the family, it's mainly the result of one or more genes that have mutated. Once a gene mutates in a person, they have a chance of passing it down to their children.
But having a particular gene mutation doesn't necessarily mean that it will result in cancer. Understanding the genetic mutations that can cause breast cancer helps you and/or your family members better understand their risk for developing breast or other types of cancer.
When Might Breast Cancer Be Hereditary?
If something is hereditary, then it runs in the family, so it can be inherited from one or both of your biological parents. But even if the person with breast cancer is a sister, brother, or your child--any of you might have gotten that mutated gene from your parents. You're twice as likely to develop breast cancer if you have an immediate family member with breast cancer. That goes up to 5 times more likely if two people in your immediate family have been diagnosed.
There's been a lot of breast cancer research over the past several decades. By comparing the genes of multiple people in one family where two or more people have been diagnosed with breast cancer, they've been able to isolate specific gene mutations responsible for hereditary breast cancer. Thanks to their hard work, people can find out if they have one or more of these gene mutations, and they can plan accordingly to reduce their risk.
And before we go any further, we want to remind you that men can get breast cancer too. They also have an increased risk associated with family history. And they can pass the gene mutation down to their children. However, only about one percent of breast cancer cases happen in men.
Breast Cancer Genetics, Explained
You don't have to be a geneticist to understand the basics of breast cancer genetics. There are mutations in two genes that science currently knows to be responsible for an increase in breast cancer risks. Those are BRCA1 and BRCA2. You may have heard them called the "Brack-uh" or "Breck-uh" genes, which is how the abbreviations are commonly pronounced in conversation.
Genes come in pairs in your DNA strands because you get one set from Mom and one set from Dad. But only one gene in a gene pair can be active, so some genes are dormant, and some are dominant. If a gene is dormant, it may do nothing right now, but you can pass it down to your kids. But if a gene is dominant, it's active in you, and you can pass it to your kids. In the case of BRCA genes, they're always dominant. That means if you have a mutation in this gene, it will always increase your risk of getting breast cancer before age 70.
Other Genes Can Increase Breast Cancer Risk Too
The scientific community's understanding of genetics has advanced in leaps and bounds since the late '90s, so a lot of our understanding is new and changing. Researchers are still trying to figure out how gene mutations increase risk and how they may work with other mutations to impact risk. They're confident that the BRCA gene mutations are the big ones to be aware of, but some others may play a role in increasing cancer risk. That includes breast cancer.
When certain mutations appear together, specific symptoms often appear together too. Researchers have labeled these groups of symptoms to better illustrate how genes play a role. Some of these syndromes associated with gene mutations include:
- Lynch syndrome linked with MLH1, MSH2, MSH6, and PMS2 genes
- Peutz-Jeghers syndrome (JPS) linked with the STK11 gene
- Ataxia-telangiectasia (A-T) linked with the ATM gene
- Hereditary diffuse gastric cancer linked with the CDH1 gene
- Cowden syndrome (CS) linked with the PTEN gene
- Li-Fraumeni syndrome (LFS) linked with the TP53 gene
You may also have increased breast cancer risk with mutations in the PALB2 gene and CHEK2 gene.
When researchers say that things are "linked" or "connected," that doesn't mean that they know the gene mutation causes the condition. It just means that based on what they know so far, some kind of association needs further research.
Who Might Benefit from Genetic Testing for Cancer Risk?
Only 1 in 400 people have mutations of the BRCA gene mutation, so it's not standard to perform this genetic test. But if you have a family history on your mother's or your father's side that matches 1 or more of the below, your doctor may recommend it:
- Anyone diagnosed with breast cancer before age 50
- Anyone diagnosed with triple-negative breast cancer by age 60
- Three or more relatives of any gender had breast cancer, ovarian cancer, pancreatic cancer, or aggressive prostate cancer
- A male had breast cancer at any age
- A female had ovarian cancer at any age
- Your heritage is Ashkenazi Jewish combined with any cancer in the family
Other compelling reasons to get tested include:
- Cancer across multiple generations on a single side of your family
- History of child or young adult cancers in the family
- Someone in the family had more than one primary type of cancer
An oncology genetic counselor can help you understand your risk factor and whether genetic testing may be a smart move for you. Genetic testing has some benefits but also drawbacks, as with any lab test that confirms something.
Pros of genetic testing:
- You can make behavioral changes to match your risk level.
- You or your doctor may recognize signs of breast cancer sooner.
- It may impact reproductive/adoption decisions.
- Your children may want to be tested based on your test results.
Cons of genetic testing:
- Knowing may worsen anxiety or depression. It's important to explore your feelings and speak with a professional in addition to your genetic counselor, if needed.
- Lack of BRCA mutations could give you a false sense of confidence.
Testing Confirms a BRCA Gene Mutation. Now What?
Stay on Top of Exams and Mammograms
Having a BRCA gene mutation doesn't mean you're definitely going to develop breast cancer, but knowing will make you and your doctors look at anything abnormal that comes up more thoroughly, just to be sure.
Your doctor may also recommend that you start getting mammograms before you usually would begin, and they may add other imaging tests on some of these visits. Those might include an ultrasound or MRI.
If you have the gene mutation, The National Comprehensive Cancer Network (NCCN) recommends:
- Continuing, or starting, self-exams
- Every 6-12 months, getting a clinical breast exam starting at age 25
- Talking with your doctor about the needed frequency for your exams
- Getting 3D mammograms
- Considering continuing breast cancer screenings after 75
Preventive Mastectomy Is Something to Consider
This is a very personal discussion, but you may consider a preventive mastectomy or ovary removal if your risk is very high because of a BRCA gene mutation combined with other factors that will be unique to your personal situation. Your genetic counselor can guide you and help you explore how you feel about this. As with all surgeries, there are risks to consider, as well. Breast reconstruction can be cost-prohibitive and may not be fully covered by insurance, so this is something to factor into the decision.
More Lifestyle Changes Proven to Lower Risk
A healthy lifestyle can reduce your risk of developing cancer despite gene mutations, so the NCCN recommends:
- Eating a healthy varietal diet with plenty of plant-foods (veggies, fruit, nuts, seeds, beans, etc.)
- Managing weight
- Meeting or exceeding CDC guidelines for physical activity, at least 150 minutes of moderate activity plus strength training
American Society of Clinical Oncology further recommends
- Keeping alcohol consumption to a minimum or none at all.
- Choosing to breastfeed, as applicable
- Finding natural ways to manage post-menopause side effects to avoid having to take hormones
Where to Start
So you think you might want to get tested for BRCA or other mutations? Meeting with a genetic counselor at Cancer Care Centers of Brevard to evaluate your personal situation and possible risk factors for breast cancer or ovarian cancer is the next step. Even if you got a test a while back when the test was new, you might want to be tested again for other gene mutations that have since been discovered. By doing so, you can better understand your risk.