Breast cancer is common, with 1 out of 8 women in the United States experiencing this in their lifetime. Surprisingly, most women who get breast cancer will NOT have a known family history of breast cancer, but up to 30% of women WILL have some family history of breast cancer, and about 10% of women having a GENETIC reason for developing their cancer. Genetic testing, therefore, is an attempt to identify a possible reason for cancer risk.
Genes are our blueprint that gets passed down from parents to child and make us who we are. Genes have a code, made from their DNA building blocks, that encodes for RNA, which in turn is translated into protein. Proteins are the functional unit of all cells. All of our genes are located on 23 separate chromosomes, so each chromosome will have thousands of genes within it. We inherit two copies of each chromosome, one from each parent, and this is how each parent may influence our traits. Just as humans are not all identical, genes can vary just as much as we do. This variation provides diversity and uniqueness for all living things.
In terms of genetics and cancer risk inheritance, if there is a gene associated with an increase in cancer risk, either because it leads to defective DNA replication, aberrant protein production, or some other downstream abnormality, this gene can be inherited from either parent and can be passed down to any child. Identifying this genetic variation for cancer risk, sometimes referred to as a gene mutation, can help select people who may be at high risk of cancer and thereby allow for enhanced screening or potential intervention to prevent cancer.
What is it?
Genetic testing requires obtaining a sample of DNA that can be found in blood, saliva, skin, or other body parts or fluids. Most genetic testing is done on blood or saliva since this is easily available. The sample gets sent to a laboratory that then isolates the DNA and sequences the particular genes of interest. Gene sequences that are “normal” and not associated with cancer risk will be interpreted as a “negative” test whereas sequences that have a variation in the DNA sequence which has been correlated to cancer risk will be reported as “positive.”
Two of the most well-known genes related to breast and ovarian cancer risk are the BRCA1 and BRCA2 genes. There are, however, over 30 genes that we know about related to various cancer predisposition risk.
Occasionally, depending on how many different genes are being evaluated, a “variant of uncertain significance” will be detected in the DNA sequence of a particular gene and this will be interpreted as such, a “variant of uncertain significance,” or VUS. As more people with this VUS are identified, the variant will, over time, sometimes after many years, get reclassified, typically as “negative” or not associated with cancer risk.
Who should get it done?
There are fairly well-established guidelines that help identify which people may be good candidates for genetic testing, but these guidelines are frequently being adjusted as we learn more about the concept of genetic risk. People who develop cancer at an early age, ie before age 50, can be identified as potential candidates for genetic testing. In some cases, if the person with the cancer is not available to be tested, first-degree relatives of the person are next in line to get tested.
What does it cost?
Before genetic testing was more readily available, the cost of the test was prohibitive to the average person, at upwards of $2000 per test. After a 2013 Supreme Court ruling that invalidated several patents on genetic testing, hereditary genetic testing for cancer predisposition genes became widely available by several companies, now with some companies offering testing as low as $249 dollars. For many people, health insurance will even cover testing if they meet requirements for testing.
Where do you go to get it done?
You should always get testing done through the oversight of a physician or genetic specialist who has background and knowledge in testing implications and can then guide you to appropriate courses of action. It is NOT advised to get testing through a “do-it-yourself” kit off the internet due to lack of guidance, regulation, quality and interpretation. Many of these tests can be misinterpreted by a lay person and lead to false assumptions of lack of cancer risk. There are many options for accessing genetic testing, and speaking first with your primary care physician or gynecologist is one good first step. Otherwise, seeking-out a genetic counselor or an oncologist who offers testing in their office is also an option.
As a Breast Surgical Oncologist, I have offered testing to my patients for many years and have even received certification through the City Of Hope in Cancer Risk Assessment program so as to better guide my high risk patients with their decisions on cancer risk management.
When is the right time to do it?
Most hereditary cancers occur after adolescence, especially breast, ovarian, and colon cancers. As such, genetic testing does not need to be done prior to age 18 for these cancer syndromes and it is generally recommended to wait until adulthood so the individual has autonomy in their decision process. Furthermore, identifying a cancer risk as such an early age can have major emotional impact without large benefit since screening for these types of cancers would not even occur until age 25 or later, depending on family history of cancer and age of onset of earliest cancer. The timing of testing is highly person and individualized, but should never be forced nor without informed consent.
Why should someone get this?
There are many benefits of testing. The most direct benefit is identifying a possible explanation for cancer development. The next real benefit is in helping people prevent cancer by taking action. For breast cancer genetic risk, for example, women can begin screening for breast cancer with breast MRI by age 25 and they can consider prophylactic bilateral mastectomy (removal of both breasts). For ovarian cancer risk, women can undergo screening with transvaginal ultrasound, blood tests and can consider prophylactic bilateral salpingo-ophorectomy (removal of both ovaries and tubes) after childbearing. For colon cancer risk, early colonoscopy and more frequent screening are available as well.
How will it impact my life?
Genetic testing can impact us in positive and negative ways. For those looking to be empowered with knowledge about risk, those who are willing to accept their risk and proceed with high-risk screening and potentially other interventions, testing can be very positive. For many, however, especially younger people who are still navigating careers, relationships, and starting families, testing can be frightening, and then knowing you carry a genetic risk for cancer can be a burden with all future life decisions, discussions, and relationships. All of these issues must be delicately considered before proceeding with testing when possible.