Have you or a relative been diagnosed with breast cancer? You may be curious about whether it runs in your family. Like many health conditions, breast cancer can have a genetic link. But this happens in only about 5 to 10% of cases. When cancer runs in the family, it's chiefly because one or more genes have mutated. Once a gene mutates, that person has a chance of passing it down to their children.
Having a particular gene mutation doesn't always mean cancer. Most people who develop breast cancer have no family history of the disease and did not inherit a gene mutation.
Understanding the genetic mutations that can cause breast cancer helps you and your family better understand the personal risk of developing breast cancer.
If something is hereditary, it can be inherited from one or both of your birth (biological) parents. You're twice as likely to develop breast cancer if you have an immediate family member with breast cancer; five times more likely if two family members have been diagnosed.
Remember that men can get breast cancer, too. About 1% of breast cancer cases occur in men, and they can also pass on gene mutations to their children. Men also have an increased risk if they have a family history of breast cancer.
Researchers have isolated specific gene mutations responsible for hereditary breast cancer. This research can help you find out if you have one or more gene mutations and let you plan accordingly to reduce your risk.
You don't have to be a geneticist to understand the basics of breast cancer genetics. Genes are short segments of DNA, and DNA holds the instructions for building proteins. Proteins control the structure, growth, and function of all the cells in our bodies.
When DNA gets an incorrect set of instructions, cells don't grow or function correctly. Any mistake in a gene will be in all the cells that contain that gene. These mistakes can be inherited, or they can happen over time as we age. It doesn't mean they will be inherited or happen over time, only that they could be.
Gene mutations that are known to cause an increase in breast cancer risk are BRCA1 and BRCA2 (BRestCAncer). You may have heard doctors call them "brack-uh" or "breck-uh" genes. Everyone has these genes, and their function is to repair cell damage and keep breast and ovarian cells growing normally.
Genes come in pairs in your DNA strands. One comes from each parent. However, only one gene in a gene pair can be active. One gene is dormant, and the other is dominant. If a gene is dormant, it may do nothing right now, but you can pass it down to your children. Dominant genes are active in you and can also be passed to your children. In the case of BRCA genes, they're always dominant. That means BRCA gene mutations will always increase your risk of getting breast cancer before age 70.
The scientific community's understanding of genetics has skyrocketed since the late 1990s. A lot of our understanding is new and continues to change. Researchers are still trying to understand how gene mutations increase risk. The BRCA gene mutations are the major ones to be aware of, but other mutations may play a role in increasing breast cancer risk.
You are much more likely to have a breast-cancer-related genetic mutation if you have any of these conditions:
Risk can also be measured as to how likely you are to develop breast cancer. The average American woman has a 12% risk of developing breast cancer during her lifetime. Having a BRCA mutation increases that from 27% up to 72%. BRCA mutations tend to develop in younger women (30s and 40s) and occur more often in both breasts, compared to women without BRCA mutations. Only 1 in 400 people have mutations of the BRCA gene.
If you have a family history on either side that matches one or more of the conditions listed above, your doctor may recommend genetic testing. A genetic counselor can help you understand the benefits of genetic testing and the drawbacks.
Having a BRCA gene mutation doesn't mean you're definitely going to develop breast cancer. However, knowing will make you and your doctors look more thoroughly at anything abnormal, just to be sure. Here are some next steps to consider:
Your doctor may recommend starting mammograms at a younger age than normal. Other imaging tests such as an ultrasound or MRI may be added.
If you have a gene mutation, the National Comprehensive Cancer Network (NCCN) recommends:
A preventive mastectomy can prevent breast cancer, especially if your risk is very high because of a BRCA gene mutation combined with other risk factors. This is a very personal discussion to have with your oncologist and genetic counselor. As with all surgeries, there are risks to consider.
Making healthier lifestyle choices can reduce your risk, such as not smoking. Other lifestyle choices that the NCCN says are linked to a lower risk of developing cancer include:
If you think you may want or need to be tested for BRCA or other gene mutations, meet with a genetic counselor. Cancer specialists will evaluate your personal situation and possible risk factors for breast or ovarian cancer. This area of medicine is changing so fast that, even if you've had genetic testing, you may need to be tested again for newly discovered gene mutations. This will help you and your doctor better understand your risk and treatment options.