Research into the heredity of breast cancer is ongoing, and we’re still uncovering the dynamics of the relationship between our genes and our chances of developing breast cancer. We do know quite a bit, however, about two specific genes that significantly increase the risk of breast cancer when harmful mutations are present. Not all women with these mutations will develop breast cancer, and not all breast cancers are due to these genetic mutations, but it’s certainly worth learning more about the so-called “breast cancer genes.”
What Are The “Breast Cancer Genes?”
The two “breast cancer genes” are known as BRCA1 and BRCA2. These genes are usually pronounced braca, and their names are simply abbreviations of the longer terms given by the researchers who discovered them: BReast CAncer susceptibility gene 1 and BReast CAncer susceptibility gene 2.
BRCA1 and BRCA2 are genes that everyone has, but some people have mutations on these genes that can greatly increase the risk of breast and ovarian cancer. These genes are known as “tumor suppressors,” and when they function normally, they help maintain cell growth at the appropriate rate. When harmful mutations are present, cells have the potential for unchecked growth, the simplest definition of breast cancer.
BRCA1 & BRCA2 Heredity
These mutations of BRCA1 and BRCA2 are hereditary, or passed along by a parent. Since we inherit two of each gene (one from each parent), that means we have two copies of BRCA1 and BRCA2. If a harmful mutation of one of these genes is inherited from a parent, every cell in the body will possess one mutated copy of the gene and one normal copy. As long as the other copy continues to function normally, breast cancer will not develop, which is why not every woman with a harmful mutation gets cancer. Her risk factor is much higher, but it’s certainly not a guarantee of breast cancer.
However, if the other copy of the gene is altered or mutated later in her life, cancer can occur. The part of the body where that second mutation occurs, such as the breast or the ovary, determines where the cancer will develop. This is a simplified explanation, and we still don’t know what exactly causes those secondary mutations, but it may be due to other biological or environmental risk factors.
BRCA1, BRCA2, and Risk Factors
Recent breast cancer statistics say that 1 in 8 women from the general population will be diagnosed with breast cancer in her lifetime. But approximately 60 percent of women who have inherited these harmful mutations will develop breast cancer. That’s 3-in-5.
Not all breast cancer is due to these genetic mutations—scientists’ best estimates suggest that only 5 to 10 percent of breast cancers are due to the mutations of BRCA1 and BRCA2. And again, not all women who have the mutation will develop breast cancer. But, more than half of them will, and many at an earlier age than the average diagnosis.
Differences Between BRCA1 and BRCA2
Although mutations on both genes are related to increased risk of breast cancer, they are two entirely separate genes. BRCA1, identified in 1990, is on chromosome 17, while BRCA2, identified in 1994, is on chromosome 13.
Both mutations increase the risk of ovarian cancer, as well as pancreatic cancer. A BRCA1 mutation can also increase the risk of cervical, uterine, and colon cancer, while BRCA2 can increase the likelihood of stomach, gallbladder, and bile duct cancer, plus melanoma.
Who’s At Risk for BRCA1 & BRCA2 Mutations?
Since the harmful mutations are inherited from either the mother or the father, family history on either side is the best indication of whether the mutation is present. Doctors will look for specific “warning signs”, including:
- Two first-degree relatives (mom, daughter, sister) with breast cancer, or if one was diagnosed at 50 or younger
- Three or more first- or second-degree relatives (including grandmother or aunt), regardless of age
- Any first-degree relative with cancer diagnosed in both breasts
- Any first or second degree relative diagnosed with both breast and ovarian cancer
- Breast cancer in a male relative
Certain ethnic groups are also at a higher risk of having these mutations, including those with Ashkenazi Jewish backgrounds, and some Scandinavian, Dutch, and Icelandic peoples. In particular, Ashkenazi Jewish people (a certain group of Central European descent) have as high as a 1 in 40 chance of possessing a harmful mutation of BRCA1 or BRCA2.
Testing for BRCA1 & BRCA2 Mutations
Testing for the BRCA1 and BRCA2 mutations is available, but can be quite expensive. Pricing usually starts at several hundred dollars and can cost as much as several thousand. Thanks to the Affordable Care Act, the tests are now guaranteed to be covered by insurance if an individual meets certain criteria in terms of family history, but those criteria are very specific and only about 2 percent of the general population will meet them.
The tests are simple blood tests that are conducted in a doctor’s office, clinic, hospital, or laboratory, and then sent to the testing company for results. It can take several weeks to receive the results, and genetic counseling both before and after the test is highly recommended. Learning about the presence of a mutation on BRCA1 or BRCA2 can be difficult, so it’s important to fully understand the implications and possible responses.
Again, a positive test result doesn’t guarantee breast cancer will develop, but it does mean your risk factor is approximately 3-in-5 instead of 1-in-8, so some sort of proactive response is recommended.
Responses to a Positive BRCA1 or BRCA2 Test Result
Women who do test positive for BRCA1 or BRCA2 have a few options. Of course, especially vigilant early detection practices should be in place, including increased monthly breast self-exams, clinical breast exams, and mammograms, all beginning at an earlier age.
Some women and their doctors may choose to undergo prophylactic surgery, which removes as much of the at-risk breast tissue as possible to reduce the chance of cancer developing in the breast. It isn’t a guarantee that breast cancer will never appear, but it definitely improves the odds. Preventative drug treatments are also available, but more study is needed to determine how useful these might be.