What is Genetic Testing?
Genetic testing is either a blood or saliva test that looks for mutations (changes) in an individual’s genes that increase their risk for developing certain hereditary cancer. Hereditary cancers are cancers where the gene mutation that increases the risk for developing that cancer is inherited from an individual’s parents. It is estimated that inherited genetic mutations are responsible for the development of five to ten percent of all cancers. The primary hereditary cancers, with medical guidelines for management, are breast, ovarian, colorectal, endometrial (uterine), melanoma, gastric (stomach), pancreatic and prostate. Whether your test results are positive or negative, the information resulting from the testing will allow your healthcare team to appropriately manage your future care. If you have already been diagnosed with any cancer, knowing whether this cancer is due to an inherited gene mutation can detect the risk of developing a second cancer and also direct your treatment and further risk management decisions. It will also provide important information for direct family members.
Predictive Genetic Testing
Predictive Genetic Testing is the most common form of genetic testing to assess cancer risk, because the hereditary gene mutation can be passed down from parent to child. There are two types of gene mutations, inherited and acquired. An inherited gene mutation is present in the egg or sperm that form the child. Since all cells in the body emanate from this first cell, the mutation is present in every cell in the body and can be passed down to children. An acquired gene mutation, not present in the egg or sperm that form the child, is acquired at a later time in life, in a particular organ, and is not passed down to children. First degree relatives (siblings, parents and children) share 50% of their genes. Predictive genetic testing is used to determine if an individual, with a strong family history of cancer, does carry inherited gene mutation.
No genetic test can show with 100% certainty that a person will develop cancer. The tests are designed to show if there is a higher risk of developing cancer, than the general population, based on evidence of the inherited gene mutation. Not all individuals with an inherited gene mutation (hereditary cancer syndrome) will develop cancer. Two persons with similar inherited gene mutations can have different outcomes. A person with a 75% risk factor might remain well and a person with a 30% risk factor might develop the disease. What is determined by the testing is that both have the potential to develop the disease and that additional screenings and other preventive actions can help to reduce those chances.
Who Should Consider Genetic Testing?
Individuals with a personal or family history of any type of cancer should consider scheduling a genetic counseling visit, particularly those with any of the following on either side of the family:
- Cancer diagnosed prior to age 50, especially breast, colorectal, or endometrial
- A combination of Ashkenazi Jewish ancestry (Jewish with ancestors from Eastern Europe, usually Germany, Poland, Lithuania, Ukraine and Russia) and breast, ovarian, or pancreatic cancer at any age.
- Two or more family members with the same type or related types of cancer*
- Two or more of the same type or related type of cancers in a patient*
*Related cancer clusters include: breast/ovarian, colorectal/endometrial/ovarian, melanoma/pancreatic.
It is important to remember that this includes both sides of your family, since your genes are passed down by both parents equally. There are many myths, such as that breast cancer can only be inherited from your mother, that are incorrect – either parent has the potential to pass down any genetic mutation that they carry.
Are There Differences in Labs Used for Genetic Testing?
There are several labs that provide genetic testing. Dr. Roberts is extremely diligent in her assessment of labs she will consider for testing done for HCC. The lab must have extensive experience specializing in genetic testing, provide results of the highest quality that can be reliably acted upon clinically, demonstrate accuracy of results through validation studies published in peer-reviewed journals and have a high-quality variant classification program that effectively communicates updated results to ordering providers. At this time there is only one lab, specializing in genetic testing, that meets our rigorous requirements.
There are home-based genetic test kits that are marketed for a number of purposes. Many of these home-based tests do not offer genetic testing for hereditary cancer syndromes and lack adequate counseling that should be performed with the testing. In addition, the FDA, that regulates the makers of genetic test kits, indicates that some of these tests are not scientifically validated. The FDA notes that genetic tests are very complex, should be performed in a specialized lab, and should not be offered without appropriate genetic counseling before and after the testing.