Genetic Testing for Cancer Susceptibility: Clinical Utility, Direct-to-Consumer Marketing, and Ensuring Results Are Properly Interpreted
Although genetic testing for cancer susceptibility is a simple process of blood sampling, the interpretation of the results may be rather complicated.
Lisa Schulmeister, RN, MN, APRN-BC, OCN®, FAAN
Editor-in-Chief OncLive Nursing
Oncology Nursing Consultant, Adjunct Assistant Professor of Nursing Louisiana State Health Sciences Center in New Orleans, Louisiana
So what’s new—and unsettling—in genetic testing for cancer susceptibility? High on my list is the clinical utility of some of these tests and direct-to-consumer (DTC) marketing. It’s concerning that personal genetic tests are heavily marketed in print ads, online, and on television, yet healthcare professionals may or may not be involved in ordering these tests or interpreting their results. On the flip side, advocates of personal genetic testing say that DTC marketing enables consumers to be proactive and better understand their family health history.
The Oncology Nursing Society (ONS), in its Position on direct-to-consumer marketing of genetic and genomic tests, notes that DTC marketing of these tests can have unintended consequences, including unnecessary and costly medical interventions, a false sense of reassurance based on negative test results, the risk of children being subjected to genetic testing, and privacy risks. It is the position of ONS that nurses integrate evidence-based genetic information into practice, educate patients and the public, and advocate for the ethical and legal use of genetic information.
Similarly, in 2010 the American Society of Clinical Oncology (ASCO) issued an updated policy statement on genetic and genomic testing for cancer susceptibility. The update was prompted by an increase in the number of these tests (>900 are now available) and raised concern about DTC marketing, as well as the unproven clinical benefit of some of these tests. ASCO advocates that genetic testing for cancer susceptibility should only be offered when the test results have accepted clinical utility, the genetic test results can adequately be interpreted, and the individual being tested has a personal or close family history suggestive of genetic cancer susceptibility.
An issue acknowledged by both ONS and ASCO is how genetic test results are conveyed to the individual undergoing testing. When the individual’s healthcare provider orders and interprets the test results, the need for the test and test results are conveyed in person and the individual has the opportunity to ask questions until he or she truly understands the implications of the results. In contrast, individuals utilizing DTC commercial testing usually self-identify the need (or perceived need) to undergo genetic testing, and these companies provide test results via a mailed or electronic report. There is no opportunity for an individual to discuss the need for, or results of, the genetic tests for cancer susceptibility.
Examples of genetic tests for cancer susceptibility with accepted clinical utility are those for BRCA1/2 for breast cancer and MLH1/MSH2 for colorectal cancer. These tests inform clinical decision-making and promote prevention or early detection of these cancers. For example, women with the BRCA1 mutation, which increases the relative risk of developing breast cancer 32-fold by the age of 40 to 49 years, can be offered increased screening or risk-reducing surgery. Individuals with the MSH2 mutation, which increases the risk for colon cancer 13.1-fold by the age of 30 years and 9.3-fold by the age of 50 years, can be offered earlier and more frequent endoscopy and a prophylactic colectomy. Similar interventions can be offered to individuals with another high-penetrance mutation, APC, which increases the risk for colorectal cancer 19-fold over a lifetime. Another high-penetrance mutation is RET, which increases the risk for medullary thyroid cancer 125-fold over a lifetime; people found to carry this mutation may be offered prophylactic thyroidectomy.
Educated healthcare providers are needed to explain the results of genetic testing and what the results mean in the context of the individual’s healthcare planning and their family members’ risk of developing cancer.
ASCO recommends that genetic tests with uncertain clinical utility, including genomic risk assessment, be administered in the context of clinical trials. However, some of these tests are already being directly marketed to the public.
Although genetic testing for cancer susceptibility is a simple process of blood sampling, the interpretation of the results may be rather complicated. Only educated healthcare providers who have interviewed and examined an individual should recommend genetic testing for cancer susceptibility to that individual, and recommend it only when it is appropriate and clinically useful. Further, educated healthcare providers are needed to explain the results of genetic testing and what the results mean in the context of the individual’s healthcare planning and their family members’ risk of developing cancer.