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How reliable are direct-to-consumer genetic tests when interpreting cancer risk?


At-home genetic testing has gained a lot of traction in recent years, raising many ethical issues. Diana Cano talked to world-leading cancer genetics expert Professor Ros Eeles to find out more about the promises and dangers of direct-to-consumer tests in helping to manage cancer risk.

Posted on 22 February, 2022 by Diana Cano

test tubes filled with blood samples

Today, our researchers shared findings that suggest the NHS eligibility guidelines for genetic testing are too stringent and causing patients, who could benefit, to miss out. This means that people with an increased risk of developing cancer could be missing out on the potential for monitoring, screening, or preventive treatment.

Since genetic testing is largely restricted to people with a sufficiently strong family history to warrant testing, it is unsurprising that those who are concerned, but do not meet the criteria, would turn to commercial DNA tests.

Increasingly, genetic tests are bought online, directly by consumers, to find out more about their DNA – a wealth of new information about their ancestry, genetic traits and risk of disease readily available at their fingertips.

When done properly, genetic testing can be an extremely valuable tool. However, direct to consumer (DTC) tests are not comparable to those used in clinical care. They are not undertaken with the same depth and quality control as medical genetic tests. But the problem is that, when it comes to understanding genetic risk, a quick at-home spit test can also be misleading and potentially dangerous.

“People often see direct-to-consumer tests as a completely accurate source of information. But one of the dangers is that these tests can lead to false reassurance,” says Professor Ros Eeles, who leads the Oncogenetics team at the ICR and is a Consultant in Clinical Oncology at the Royal Marsden

BRCA1 and BRCA2 variants

For example, think of BRCA1 and BRCA2 – genes often associated with increased risk of breast and ovarian cancer. Direct to consumer tests that screen for these two genes often only look for a few variants out of the more than one thousand BRCA variants linked to disease.

Different ‘variants’ mean different genetic alterations that increase someone’s predisposition to cancer. So when some DTC tests conclude you don’t have any genetic alterations that increase your risk of breast cancer, what they mean is that you don’t have any of the alterations they test for – around three out of a thousand. Additionally, these tests can also give an incorrect result because of the way the technology works.

This means people can be wrongly reassured that they are not carriers of a BRCA mutation linked to disease, and they might decline undergoing breast cancer screening as a consequence.

There is also the danger of false positives. According to The Royal College of General Practitioners (RCGP) and the British Society for Genetic Medicine (BSGM), DTC tests that use the “SNP chip” technique – used by the majority of DTC testing companies – are very likely to categorise rare variants wrongly. For example, 85-95 per cent of BRCA1/2 variants or bowel cancer gene variants are likely to be false positives.

The take-home message is simple: DTC tests should not be used as a substitute for seeing your doctor for cancer screenings or counselling when it comes to genetic factors that can increase or decrease cancer risk.

90S study

Our researchers, led by Professor Ros Eeles, are carrying out the 90S study to explore the use of regular genetic testing as part of health screening in the general practice setting. If successful, the study could be a key step towards much more routine use of genetic testing to predict and manage patients’ health within the NHS. They have spent years developing and planning the logistics and every step of the whole-genome sequencing process to make it safe and accurate.

“We are working to screen the genomes of around a thousand GP patients in London, at The London Genetics Centre at 90 Sloane Street (, to assess the feasibility of testing for faulty genes that increase the risk of cancer and heart disease. The testing also looks at genetic variants that are important in family planning and for how we process medications. What we are undertaking is a pioneering study to assess how whole genome screening could be used in the future as part of a medical screen in primary care in adults,” explains Professor Eeles, who co-leads the 90S study with Dr Michael Sandberg, a GP and honorary clinical fellow at the ICR.

A whole genome sequencing test consists of a blood test, analysed in specialised laboratories. Sequencing in this way is more accurate than the technology which is used in most DTC tests.

All results are then assessed by consultant geneticists – and abnormal results are discussed at a multi-disciplinary meeting of several consultant geneticists together with the GP.

Researchers also want to understand what impact the genetic information has on patients. For this reason, people who participate in the trial have access to genetic consultants and staff for psychological support who can help communicate the findings so that patients and their families can make independent decisions based on their genetic information.

The importance of genetic counselling

The impact unregulated genetic information can have on people is part of the reason DTC genetic testing has triggered a debate over the clinical value and legitimacy of these tests. In fact, last year, the House of Commons Science and Technology Committee released a report calling for the UK Government to update existing regulations for DTC tests.

They specifically called for regulations to protect consumers – for example, in the form of adequate counselling and consent processes. In other words, they encouraged the UK Government to revise regulations regarding the advice and support offered to people when they buy DTC genetic tests. One of their suggestions was to make it a requirement for these companies to provide genetic counselling to consumers.

After all, for genetic information to be valuable to patients, it needs to be communicated properly. It is not as valuable if people lack a proper understanding of their risk factors and what they can do to help mitigate some of the risks.

Cancer screening

Screening is something that can help clinicians when managing patients at increased risk of cancer. Having a better understanding of inherited faulty genes linked to cancer also means we can better target cancer screening to those who need it the most. This is how clinicians manage patients at higher risk – with the help of targeted screening programmes.

When done properly, being able to identify those at higher risk is a huge opportunity that could save many lives by spotting cancer early on – when the chance of cure is higher.

At the ICR, Professor Ros Eeles and her team are working to find out if knowing more about genetic changes linked to cancer can improve prostate cancer screening for men at an increased risk. Their hope is not only to develop screening programmes, but also to improve the tests that may be used for screening.

An example is the IMPACT study, which recently found that men who inherit an increased risk of cancer through ‘Lynch syndrome’ could benefit from regular PSA testing from age 40 to detect early signs of prostate cancer.

The PROFILE trial also seeks to develop new and better tests to screen patients with genetic changes linked to prostate cancer and detect the disease earlier. PROFILE is also a first-of-its-kind study in the UK in aiming to solve the mystery of why Black men develop prostate cancer at twice the rate of other men in the UK.

Prostate cancer screening saves lives. Help us continue to find new ways to defeat prostate cancer – and improve the chance of survival for men with this disease. Please make a donation today.

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Reviewing regulations

So, while at-home genetic tests are gaining popularity, they also pose challenging ethical questions. Can they provide people with the information they need to understand their results? Are these companies obtaining appropriate informed consent?

“I would urge the Government to review regulations for commercial DTC tests – we need some kind of regulatory framework. People can easily misconstrue the results of these tests, which are designed for interest purposes only. They are not medical tests and can lead to false reassurances for those who could be at genuine risk of cancer.

“When it comes to cancer risk, quick and easy can also mean inadequate and potentially dangerous, which is why I would also urge the NHS to broaden its gene testing eligibility guidelines,” says Professor Eeles. “Medical genetic testing should not be a luxury; it can save lives and should be accessible to those who need it.”


genetics Ros Eeles DNA screening gene testing
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