Thanks to advances in genetics and technological progress, it is now possible to detect our predispositions to develop some diseases. What are the benefits of being informed of our future fragilities? And what are the abuses to watch out for? Current high-throughput genome sequencing techniques, capable of rapidly deciphering the DNA found inside our 70 trillion cells, are paving the way for tailor-made predictive medicine. They make it possible to reveal whether some of our genes carry mutations likely to induce serious diseases.
But it is still necessary to be able to interpret the results correctly because who says risk factor does not necessarily say occurrence of the disease. And for these data to be useful, a prevention or early treatment strategy must be put in place. In France, these genetic tests are strictly supervised, but this is not the case in all countries where DNA has become a lucrative business... with sometimes questionable ethics.
"More than 8000 diseases due to an anomaly on a gene have already been identified", specifies Pr Pascal Pujol, president of the French Society of Predictive and Personalized Medicine (SFMPP) and author of Do you want to know what our genes say about our health* (ed. Humen Sciences).
But rare are those where the presence of this anomaly leads for sure to the development of the pathology. This is the case of Huntington's chorea, which causes neurological degeneration from the age of 30, sometimes even much earlier and for which we still have no treatment. In families at risk, prenatal screening is offered because inheriting a single copy of the faulty gene is enough for the condition to manifest itself inevitably.
Video of the day:However, in the majority of cases, genes are not everything. Several genes interfere, as well as the environment in which we live, the state of the intestinal flora, etc. Carrying a gene predictive of these diseases simply corresponds to an excess risk compared to the general population. Diabetes, certain common cancers, autoimmune diseases are thus called multi-factorial diseases.
When several members of the same family develop early breast cancer, genetics may be involved. Certain mutations of the BRCA1 or BRCA2 genes, which theoretically contribute to repairing damaged DNA, are then suspected. The women concerned can benefit from genetic tests, via an oncogenetic consultation.
Knowing that you are a carrier of these altered genes is not useless since effective prevention measures can be put in place. In 2013, actress Angelina Jolie chose to undergo a double mastectomy for preventive purposes, followed two years later by the removal of the ovaries and fallopian tubes to prevent the appearance of future cancers.
Fortunately, other alternatives exist, because not all patients with these genes will necessarily declare cancer. "The BRCA1 gene gives a 70% risk of developing breast cancer and 30% ovarian cancer", explains Professor Pujol.
A personalized screening program can therefore be set up for breast cancer, with close follow-up every year – or every 6 months if necessary – from the age of 30. As for the ovaries, preventive surgery can be a good option once the pregnancy plans have been made, as screening for ovarian cancer is more difficult.
Developed by Predilife, an offshoot of the Gustave Roussy Institute, the Mammorisk software assesses the individual risk of breast cancer from the age of 40 on the basis of clinical data, medical imaging and genetics. Depending on the risk score obtained, the doctor establishes a specific screening schedule, with the type of examinations necessary and their frequency over 5 years.
This innovative prediction test, offered at the Paris Breast Institute, the Santa Maria Institute in Nice and the American Hospital of Neuilly/Seine, is particularly interesting for women under 50 for whom a mammogram is not is not scheduled every 2 years as part of the national organized breast cancer screening program. It also allows you to adopt a preventive lifestyle (control your weight, quit smoking, get back to sport, etc.) because we know that these factors considerably reduce the probability of cancer, especially in women who present a high genetic risk.
Similarly, screening at birth for a deficiency in MCAD, a hereditary disease which has just been added to the five other pathologies systematically screened for in newborns, makes it possible to carry out active prevention. For this pathology characterized by an inability to metabolize short-chain fatty acids, an appropriate diet helps to avoid complications (developmental disorders or sudden infant death syndrome).
In many cases, the forecast is useless… except to distress the person who fears the sword of Damocles identified above his head. What good is it to know that you have an increased susceptibility to a disease if you have no lever for action to reduce your risk and no treatment likely to block your way?
And what's the point of worrying about a risk that will probably never come true. Some susceptibility genes are non-specific or remain silent throughout life.
A genetic variant is found, for example, in 80% of patients with celiac disease, an intestinal pathology triggered by the ingestion of gluten. Certainly, but this variant also exists in many people who do not suffer from this disease. An important nuance that commercial genetic prediction tests pay little heed to.
In France, genetic tests can only be carried out within a fairly strict framework, either under medical prescription or at the request of the courts, by approved laboratories. But in other countries, such as the United States, the United Kingdom or Brazil, they are freely available.
Many companies have invested in this very lucrative market. Nearly 100 million people worldwide have already used it, according to the MIT Technology Review . Although this is strictly prohibited in France (€3,750 fine), more than 100,000 French people have bought it on the Internet.
You can find everything on the web:test to determine the geographical origin of your ancestors, test for predisposition to different cancers, Alzheimer's disease, diabetes... All you have to do is take a few cells from your mouth using a a swab received by mail and send this sample to the laboratory to receive its results a few days later.
"All these tests are not reliable, believes Professor Pujol and they do not offer any medical support, which is really regrettable."
Commercial genetic tests – known as “recreational tests” – present another pitfall:the client hands over all the information contained in his genome to a foreign private company. In Europe, genetic data is considered personal and protected by the General Data Protection Regulation (GDPR), but not across the Atlantic. The companies to which you have transferred them - the contract generally stipulates this in very small print - make multiple uses of them, such as reselling them to pharmaceutical manufacturers for example.
This data can also be hacked, as was the case with millions of MyHeritage company user accounts. If they end up in the hands of your bank or your mutual health insurance, what could be the consequences? Could your potential vulnerabilities become an argument to deny you a loan or increase your annual dues? All drifts are possible.
* Available on Place des libraires and Amazon.
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