Understanding the alphabet soup of genetic testing for cancers
Kathryn E. Vinson, MS, CCRC
The world of cancer research was forever changed with the advent of the first genetic test for breast and ovarian cancers in 1996 – the BRCA1 and BRCA2 tests. But what do these abbreviations mean? How do they cause cancer? If I come up positive for one of these mutations – does it mean I will get cancer? Let’s sit back, have a bit of a biology lesson, and discuss what these tests mean for us – both men and women.
What is BRCA?
The abbreviation here is quite simple – BReast CAncer susceptibility gene; however, the genetics and outcomes of these two genes are a lot more complicated. There are two different known BRCA genes – BRCA1 is located on chromosome 17 and BRCA2 is on chromosome 13. These are what are called autosomal chromosomes, not the sex chromosomes that we know as X and Y. We each carry two copies of these genes, one from our mother and one from our father. If one of our parents has a mutation in one of these genes, they have a 50% chance of passing it on to each of their children.
The BRCA genes are known as tumor suppressors. When they are functioning properly, they help repair DNA damage that can cause cancer, but when certain mutations are present, they cannot make these repairs. In other words, mutations of the BRCA genes do not cause cancer, rather they prevent the body from stopping cancer.
Cancers linked to BRCA
Most of us are aware of the link between BRCA mutations and both breast and ovarian cancers, but other cancers are also known to proliferate when these mutations are present. In ladies, we see fallopian tube cancer and peritoneal (the lining of the abdominal cavity) cancers, and in men, breast cancer and prostate cancer. Below, I have compiled a table showing the chances of developing some of these cancers when these mutations are present. Bear with me in that some data is shown as percent risk and some as increased risk – this data was taken from several sources.
|Breast – female||Ovarian||Breast – male||Prostate|
|BRCA1||72%||44%||3.8x normal risk|
|BRCA2||69%||17%||8% (normal is 1%)||8.6x normal risk|
Other cancers with increased risks are colorectal, melanoma, and pancreatic. For those children that inherit a specific BRCA2 mutation from both parents, they are likely to have Fanconi anemia, which has been linked to solid tumors and acute myeloid leukemia in kids. Interestingly, it has been shown that having mutations on both genes does not increase the risk over one mutation, nor does it change risk based recommendations from the medical community.
Should I get tested?
Much like testing for genetic diseases like Huntington’s Disease, it is a very personal question with a lot of factors that go into it. The KnowBRCA tool is suggested by the CDC to help you understand your chances of having an inherited BRCA mutation. It is also worth mentioning that under the Affordable Care Act, US insurance companies are required to pay for BRCA testing if you meet the criteria set forth by the United States Preventive Services Task Force. The National Cancer Institute provides the following guidance for possible testing (directly quoted):
- Breast cancer diagnosed before age 50 years
- Cancer in both breasts in the same woman
- Both breast and ovarian cancers in either the same woman or the same family
- Multiple breast cancers in the family
- Two or more primary types of BRCA1– or BRCA2-related cancers in a single family member
- Cases of male breast cancer
- Ashkenazi Jewishethnicity
If you feel that this testing is right for you, talk with your doctor about it. He/she can guide you in this decision, as well as what measures you will or won’t take should your results show a mutation.
If you have already been diagnosed with one of these forms of cancer, testing can help your oncologist prescribe the correct treatment for your disease. You may also want to provide your status to genetically related family members. A genetic counselor and/or your oncologist can help you with these decisions.
For those of you that have been affected by BRCA linked cancers, there are a lot of resources available to you and your loved ones. From financial help, to caregiver assistance, to the emotional support found in Closed Facebook Cancer Groups, there are many people our there that would love to help you in your fight.