DNA Testing For Cancer Genetic Susceptibility Genes

There are a growing number of genes being discovered that predispose a person to developing cancer for which testing is clinically available. Due to the complexity of the testing and the issues surrounding testing, the American Society of Clinical Oncology (ASCO) has published guidelines on when to offer cancer predisposition testing to patients. These guidelines were most recently updated in 2010.

ASCO recommends that cancer predisposition testing be offered only when:

  • The individual has personal or family history features suggestive of genetic cancer susceptibility

  • The genetic test can be adequately interpreted

  • The test results will help with the diagnosis, treatment, and/or management of the patient and family members at risk for cancer 

However, ASCO also acknowledges that emerging technologies, like genomic profiling for low penetrance genetic variants (markers of very low disease risk), may be appropriate for some patients who do not have a personal or family history that suggests a higher risk of cancer. People may undergo genetic testing using direct-to-consumer (DTC) tests, but they may ask their health care providers for help in interpreting the test results and obtaining follow-up care. For any genetic test, ASCO urges doctors and other health care providers to recommend follow-up care that is based on established cancer risk factors such as family history, behavioral factors, environmental exposures, and scientifically-validated tests for cancer risks. 

ASCO further states that although the list of genes for cancer susceptibility syndromes continues to grow, the ever-changing nature of the field highlights the importance of getting genetic counseling both before and after doing genetic testing. Companies that offer DTC testing should provide this counseling or refer people to independent providers of these services. 

In general, a definitive genetic test result may have considerable medical and psychological significance. A negative test (finding no mutation) in a family with a known gene mutation may provide significant relief regarding personal cancer risk and the risk to one's children, and may help these people avoid unnecessary medical or surgical interventions. A positive test may lead to earlier or more frequent surveillance, consideration of prevention options, and may influence disease management.

But genetic testing may also pose several risks. A positive genetic test and subsequent interventions may cause the patient or family distress. A negative test (not finding a known mutation in the gene analyzed) may result in undue reassurance for a person who may still be at markedly increased cancer risk based on their family history. Furthermore, some test results may be unclear, which may be frustrating or lead people to the wrong conclusions. It is very important that people have a good understanding of what the tests may or may not tell them before they have them done.

Because of the medical, social, and legal ramifications associated with genetic test results, ASCO strongly recommends that genetic testing be done only when paired with pre- and post-test counseling. This ensures that patients are aware of the potential implications of their test results in the context of their decision of whether to seek testing. Full discussion after testing will also ensure that patients make informed medical decisions on receipt of test results.