Three things to know about direct-to-consumer breast cancer genetic testing
Access to genetic testing is constantly evolving. With a simple cheek swab, people can receive information about many different traits, including some risk information about hereditary breast and ovarian cancer (HBOC) syndrome. With more people getting this information, here are some tips for understanding and using the results.
Consider the following two patients, who have both recently chosen to receive results about their breast cancer risk through a direct-to-consumer (DTC) testing (or “personal genomics”) company. These cases highlight some important benefits and limitations of BRCA1/2 testing available direct-to-consumer.
Beth, 53, has received results that indicate she does not carry any of the mutations related to HBOC tested by the company. She feels relieved because her mother and aunt both had breast cancer under the age of 50 and her sister recently died from ovarian cancer in her early 50s.
Gina, 31, received results that indicate she has a mutation that puts her at a much higher risk for developing breast and ovarian cancer. She is very surprised because no one in her family has had cancer. She isn’t sure whether she should believe the results.
Tips for Understanding and Using the Results
1. Before using DTC test results (positive or negative) to make clinical decisions, results need to be confirmed in a clinical lab on a new sample.
There is a chance the DTC methods used can result in a false positive or false negative, so it is important to confirm the result on a fresh blood sample. Genetics experts can help determine the appropriate testing to confirm the results, as well as evaluate personal and family history to determine level of risk and whether additional testing is needed.
2. Negative results on DTC testing are not definitive; additional testing may be needed if there is a clinical indication of higher risk.
Beth was reassured by her negative results on BRCA1/2 testing. However, it is important to note that the test she received assessed for only 3 of the thousands of variants in these genes known to be associated with hereditary breast and ovarian cancer syndrome (HBOC). While she can be reassured that she does not have one of the 3 mutations tested, these results do not reduce her risk significantly. Because testing was not sufficient to assess her risk, she remains at the high risk indicated by her family history.
Clinical evaluation and testing for HBOC typically starts with assessing a detailed family history to determine the level of risk and appropriateness for testing. With someone who has already had some testing, like Beth, it is important that the provider review the report to determine what testing has been done and whether it assesses the appropriate variants. Depending on the situation, an individual may need to be tested for a panel of 20 or more genes or, if the mutation causing cancer in the family is known, a single mutation. Given Beth’s strong family history of breast and ovarian cancer, additional genetic testing is likely needed to determine whether or not she is at high risk of developing cancer. She should talk with a genetics expert to further clarify her risk and discuss whether and how to proceed with additional genetic testing.
3. Positive results on DTC testing can help identify individuals who did not know they were at risk.
Gina was surprised by her positive results on BRCA1/2 testing, especially because she did not know of anyone in her family that had been diagnosed with cancer. Not everybody with HBOC has a strong family history of breast and/or ovarian cancer, which is typically what is warranted to get genetic testing ordered by a clinician. People may have small families, not talk with all or certain relatives about health issues, or be adopted. In these cases, there may not be enough information to determine if someone is at increased genetic risk.
Receiving a positive result, either expected or unexpected, provides the opportunity to take action to identify cancer early and reduce risk. All clinically relevant results from DTC testing need to be confirmed in a clinical lab before taking any action. Once confirmed, there are clinical guidelines for increased cancer screening and options to reduce risk patients can follow. Genetics experts can help in the process of confirming results and outline screening and risk reduction options.