Breast cancer researcher warns against online genetic tests

June 18, 2018 by Kate Wighton, Imperial College London
Paul Thiruchelvam, breast cancer researcher and surgeon, says online tests may be misleading. Credit: Imperial College London

We have never been so fascinated by the secrets inside our cells.

Tests that analyse our genetic make-up—the DNA packaged inside every cell of the human body – are more popular than ever.

Requiring just a swab of saliva, some kits offer a peek into the past, and tell you where your ancestors hailed from. Others provide information closer to home, and reveal whether you carry that increase the risk of disease.

DNA analysis firm 23andMe recently gained approval from the U.S Food and Drug Administration to launch a kit that tests for gene mutations that increase the risk of and .

The company hailed the decision as a "milestone in consumer health empowerment".

So do these online tests mark a leap in cancer prevention? Not according to Paul Thiruchelvam, a breast cancer researcher and surgeon from Imperial's Department of Surgery and Cancer. He wrote recently in The Lancet medical journal that these tests could be misleading—and potentially harmful. Here he explains why.

What are your concerns about these tests?

Our biggest concern with this direct to consumer is the potential for false reassurance.

Up to one in five breast cancers are thought to be due to faulty .

In many cases, these faults are in two genes—BRCA1 and BRCA2.

Faulty copies of these BRCA genes results in a 40 to 70 per cent lifetime risk of breast cancer, compared to a 12 per cent risk in the general population.

Moreover, the risk of ovarian is 20 to 55 per cent with a faulty BRCA gene, compared to 1 to 2 per cent in the population.

Whilst 23andme can detect a BRCA1/2 mutation with high accuracy and precision, a major caveat is that they only test for three possible faults or mutations out of more than a thousand mutations in the BRCA genes that raise cancer risk.

Furthermore, the three mutations it looks for are most commonly found in the Ashkenazi Jewish population, but rarer in other populations.

A negative result means that the individual will not have these three BRCA1/2 mutations, but they may have others.

Additionally, there many other types of faulty genes—aside from BRCA1 and 2—that can increase such as ATM, CHEK2, PALB2, PTEN and TP53, yet the 23andMe kit doesn't test for these.

Up to one in five breast cancers are thought to be linked to faulty genes. Credit: Imperial College London
So these tests don't provide a complete picture?

Exactly. Imagine the scenario: someone's relative has recently been diagnosed with breast cancer, and they decide to take the online test. The results tell them they don't carry the faulty BRCA gene, and they may be false reassured by the negative result.

Armed with these test results, this individual may not be as vigilant at looking for breast cancer symptoms as they should be. They may have one of the many other faulty cancer genes the online kit doesn't test for and they simply would not know.

However, if they were to avoid this test and go straight to their GP, they could be referred to a specialist. Their doctor may be able to arrange regular checks if required—called surveillance—to monitor for any signs of cancer.

Is genetic testing available on the NHS?

Yes. If a person is worried about their cancer risk a trained healthcare professional will be able to take a thorough , and then, if appropriate, refer them for genetic testing. These tests, unlike the online test, test for many mutations in the genes linked to breast cancer.

If a patient is found to have a faulty gene—what next?

This is another concern. In our clinic, when a patient is found to carry a faulty gene, they will see a genetic specialist who will counsel them of their cancer risk before testing and advise them of their options in the event of a positive result.

23andMe customers are signposted on the website to a genetic counsellor but an individual receiving these results online will not have immediate support or guidance.

This is what we're starting to find in clinic—my colleagues are seeing patients who have taken the online tests, are having difficulty interpreting their results, and they don't know whether the implications are positive or negative.

What's your view on these tests?

There is no doubt the online genetic test market will continue to grow as the price of testing reduces. Genetic tests have transformed cancer treatment—and will continue to improve patients' lives.

There is no doubt that other models of genetic testing need to be explored to overcome the shortcomings of current models of testing.

Many experts believe all patients should be tested—regardless of family history. This is because studies have demonstrated that only half of BRCA-positive cancer patients have a strong family history.

At the moment, if an individual doesn't achieve a threshold for testing based on a history of family members with breast or ovarian cancer they may not receive genetic testing. This means a potential BRCA mutation would be missed.

Other cancer specialists have gone one step further and predict whole population testing for faulty genes in as little as ten years.

Whilst online testing enables democratisation of health information and empowers people to take control of their lives and potential risks, it also means that data is being given to individuals who might not be adequately prepared to hear it.

Although people may think they are doing themselves a service by taking these tests, they are actually doing themselves a great disservice.

"Pervasive " by Paul Thiruchelvam, Carla Fisher, Daniel Leff and Susan Domchek is published in The Lancet

Explore further: Despite risk of breast cancer, few men undergo genetic tests, study finds

More information: Paul T R Thiruchelvam et al. Pervasive genetic testing, The Lancet (2018). DOI: 10.1016/S0140-6736(18)30997-8

Related Stories

Despite risk of breast cancer, few men undergo genetic tests, study finds

June 1, 2018
Cancer is one of the leading causes of death among Americans. At least 10 percent of cancers are caused by inherited mutations in genes such as BRCA1 and BRCA2. Parents with the cancer gene mutation have a 50 percent chance ...

Busting myths surrounding cancer and genetic testing

April 13, 2018
(HealthDay)—While only 5 percent to 10 percent of cancers are caused by an inherited gene mutation, genetic testing may benefit people with a strong history of family cancer, an expert in genetics suggests.

Beyond BRCA: Links between breast, second primary cancer and inherited mutations

May 31, 2018
Rates of inherited mutations in genes other than BRCA1/2 are twice as high in breast cancer patients who have had a second primary cancer—including, in some cases, different types of breast cancer—compared to patients ...

Breast cancer genes a real risk for men, too

April 26, 2018
(HealthDay)—Few American men are screened for gene mutations that can greatly increase their risk of breast and other types of cancers, a new study reveals.

Genetic predisposition to breast cancer due to non-brca mutations in ashkenazi Jewish women

July 20, 2017
Genetic mutations in BRCA1 and BRCA2 increase the risk of breast and ovarian cancer in Ashkenazi Jewish women. A new article published by JAMA Oncology examines the likelihood of carrying another cancer-predisposing mutation ...

As genetic testing for breast cancer gene mutation expands, questions arise about treatment decisions

May 3, 2018
The Food and Drug Administration recently announced its authorization that permits genetics testing company 23andMe to market a test for gene mutations associated with risk of breast and ovarian cancer.

Recommended for you

Pancreatic cancer's addiction could be its end

November 13, 2018
Cancer cells are often described as cells "gone bad" or "renegade." New research reveals that in some of the deadliest cases of pancreatic cancer, these rebellious cells have an unexpected addiction. Now, scientists are investigating ...

Cognitive decline—radiation—brain tumor prevented by temporarily shutting down immune response

November 13, 2018
Treating brain tumors comes at a steep cost, especially for children. More than half of patients who endure radiation therapy for these tumors experience irreversible cognitive decline, a side-effect that has particularly ...

Study finds promising therapeutic target for aggressive type of breast cancer

November 13, 2018
A new Nature Communications study led by University of Kentucky Markey Cancer Center researchers suggests that an enzyme known as Prolyl 4-hydroxylase subunit alpha-1 (P4HA1) is a potential therapeutic target for triple negative ...

Solving the mystery of NPM1 in acute myeloid leukemia

November 13, 2018
Although it has long been recognized that mutations of gene NPM1 play an important role in acute myeloid leukemia, no one has determined how the normal and the mutated forms of the protein NPM1 function.

Scientists shine new light on link between obesity and cancer

November 12, 2018
Scientists have made a major discovery that shines a new, explanatory light on the link between obesity and cancer. Their research confirms why the body's immune surveillance systems—led by cancer-fighting Natural Killer ...

Obesity both feeds tumors and helps immunotherapy kill cancer

November 12, 2018
A groundbreaking new study by UC Davis researchers has uncovered why obesity both fuels cancer growth and allows blockbuster new immunotherapies to work better against those same tumors.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.