Cancer Screening: Genetic Testing
Genetic cancer screening at a glance
- Genetic cancer testing screens individuals for genetic mutations that may cause cancer later on in life.
- Those with a family history of cancer or who are at increased risk of carrying genetic defects may elect to have their genes tested for cancer mutations.
- Predictive gene testing is the most common type of genetic test done to assess cancer risk.
- DNA samples are typically gathered from blood or saliva, and it takes about a month to get the results.
What is genetic cancer screening?
Genetic cancer screening evaluates a person’s risk for inheriting a cancer caused by a genetic mutation. Between 5 and 10 percent of cancers are linked to genetic causes. Genetic testing is a relatively new technology now more commonly available due to advances in mapping the human genome that have brought down associated costs and time constraints. Genetic testing can evaluate risk for hundreds of medical issues, including cancer.
Predictive gene testing is a specific test most often used to check for gene mutations that increase an individual’s risk for cancer. Predictive genetic testing is done for people whose families have a history of cancer because that makes it more likely that the cancer-causing gene may be inherited. For example, if a woman’s mother or sister has had ovarian or breast cancer, she may be tested for the BRCA1 and BRCA2 genetic mutations known to cause those cancers.
Hereditary gynecologic cancer syndromes (HGCS) are a collection of genetic causes of gynecological cancers. Individuals with HGCS inherit an established risk of getting certain cancers. The most common and noteworthy hereditary gynecological cancer syndromes include BRCA1 and BRCA2 mutations. Lynch syndrome is another HGCS, which increases the risk of endometrial and ovarian cancers.
Hereditary cancer is indicated by cancer diagnosis at a young age and patterns of cancers within a family. Cancers that may be caused by genetic factors include:
Types of results from genetic testing
Genetic testing is usually conducted by taking a blood, saliva or skin cell sample. A genetic testing laboratory then analyzes the sample and returns the results to the doctor or genetic counselor who requested the test. Several weeks are usually required to compile and deliver the results back to the patient.
Test results can be positive, negative, uninformative negative, false negative or positive, variant of unknown significance, or benign polymorphism.
- Positive result may confirm a diagnosis, indicate that a person is a carrier of a particular genetic mutation, or identify an increased risk of developing a disease (such as cancer) in the future. Sometimes the positive response merely suggests a need for further testing.
- Negative result may mean no mutation in the gene.
- Uninformative negative means there was no change or mutation in the tested gene. This result neither confirms nor rules out a result and typically requires more testing.
- Variant of unknown significance, as it sounds, means the results are inconclusive as to whether the genes will cause a mutation and resulting cancer mutations.
- Benign polymorphism means that the variation in the DNA is too common to be only caused by a mutation and occurs in at least 1 percent of the population.
- False negative/positive occurs when there is an error in the test and it either conveys a negative result when there is, in fact, a mutation, or it reveals a positive result when there is, in fact, no mutation.
Genetic cancer screening considerations
Genetic cancer screening reveals the chances of getting cancer and allows patients to be proactive in their health by looking to confirm if they do have a drastically increased risk of cancer. Those wanting to be screened for genetic cancers should speak with a professional who specializes in the issue, such as a genetic counselor, before deciding.
Genetic testing is a unique medical test that not only screens the patient, but may also indicate genetic information about the patient’s relatives. If there is a confirmed genetic mutation in a patient, his or her relatives have a much higher chance of carrying the same genetic syndrome.
Genetic cancer testing is not the best choice for everyone. A genetic counselor helps each patient make the more informed and appropriate decision. For individuals who would like to test their genes for cancer risk, the counselor will evaluate the chance of genetic mutation and generally estimate personal risks to the patient before making a recommendation to move forward or not.
Individuals should consider the many ethical, social and legal issues related to genetic cancer screening. For example, what will a patient do with the test results? What duty does the patient have to inform all family members and what effect will that have? Genetic counselors are often needed to address such issues.