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The pitfalls of direct-to-consumer (DTC) cancer genetic testing

The pitfalls of direct-to-consumer (DTC) cancer genetic testing

A recent article in the British Medical Journal1 (https://www.bmj.com/content/367/bmj.l5688) has raised concerns about the reliability of online direct-to-consumer (DTC) genetic tests that promise information on ancestry, athletic performance and disease risks. These tests, usually performed on a saliva sample, are often unvalidated and unregulated and users need to be aware that there may be a significant risk of false-positive and false negative results with some providers. I want however to focus on the pitfalls of using DTC cancer genetic tests, and how these can be addressed.

Genetic testing is advised at the diagnosis of breast cancer for those women with particular tumour characteristics and/or a strong family history of breast and/or ovarian cancer, and the most common mutations occur in either the BRCA1 or BRCA2 genes. Normally, these mutations are looked for using a method called Next Generation Sequencing (NGS) that analyses the DNA over and over again to look for changes (variants) that might be real mutations. If in doubt, these variants can be compared to up to date databases that classify them as harmful or not. Unless this level of analysis and scrutiny is used in the DTC BRCA tests, then false positive and false negative results can arise and lead to wrong treatments or unnecessary clinical interventions. Users should therefore ensure that they use a trusted and reliable genetic testing company that they can talk to for advice about the limitations of the test prior to testing, and that can provide professional clinical support at all points of the genetic testing pathway.

The other major criticisms of DTC cancer genetic tests is that the results can be complicated and easily misinterpreted, and that there is no easy access to genetic counsellors to help explain the expectations prior to testing and the results and next steps after testing. A recent publication has reported that BRCA testing on all women when diagnosed with breast cancer, rather than just those with a strong family history, is more cost-effective(https://jamanetwork.com/journals/jamaoncology/fullarticle/2752373). Therefore, genetic testing is going to become more and more prevalent for optimal selection of personalised cancer treatment based on genetic analysis of the tumour itself, and genetic counsellors will become increasingly involved in these complex discussions both before and after genetic testing. It is therefore imperative that this specialty is recognised and expanded within the NHS, and recognised and reimbursed by private medical insurance companies in the UK.

At GeneHealth UK (www.genehealthuk.com), part of the Check4Cancer group, we have a nationwide team of genetic counsellors who support our cancer genetic service for breast, ovarian, bowel and prostate cancer with interpretation of the NGS raw data by our own team of genetic scientists. In this way, we can reassure clients and patients that they will only have testing that is appropriate and validated, and that we will provide professional clinical support after testing, whether the test is positive or negative.


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