On 26 June 2000, the then President of the United States, Bill Clinton, presented the first draft of the human genome at the White House, alongside Tony Blair (then Prime Minister of the United Kingdom) and researchers Francis Collins and Craig Venter. At that event, the former president stated that this information would provide humanity with a tool capable of enabling unprecedented precision and personalisation in the treatment and prevention of disease, marking the starting point of personalised medicine.
More than 20 years later, one might think that this promise has yet to be fulfilled, since, after all, our doctor has never asked about our genetic information during a routine check-up.
Personalised medicine
However, this is not the case. Personalised medicine, also known as genomic medicine or precision medicine, has transformed how we diagnose and treat certain diseases. For example, today we know that there is not just one single “breast cancer”, but rather that this disease can be classified into eight subtypes based on its molecular signature, that is, the combination of different genetic and epigenetic factors.
Each cancer subtype has a different prognosis and requires a different treatment, enabling the development of new therapeutic targets and more targeted drugs. This helps avoid the need for non-specific treatments such as broad chemotherapy, which exposes the body to multiple drugs in the hope that one might work.
Another example comes from next-generation sequencing, which has changed how we understand assisted reproduction through carrier screening. This type of DNA test makes it possible to identify whether a healthy couple, despite never having shown signs of a genetic disorder, could pass on a combination of genetic material to their children that might lead to serious diseases such as cystic fibrosis, alpha-thalassaemia, or various metabolic disorders.
In the field of reproduction, we have also seen how non-invasive prenatal testing (NIPT) makes it possible to rule out the presence of genetic conditions or abnormalities such as Down syndrome by analysing fragments of the unborn baby’s DNA from a blood sample taken from the mother, without the risk to the fetus associated with amniocentesis.
Therefore, we can say that the promise of genomic medicine has indeed been fulfilled, at least in certain specialties such as oncology, assisted reproduction and rare diseases, where genetic testing has already become an essential technique incorporated into routine clinical practice.
At this point, a natural question arises: if genetics can already be effectively integrated into healthcare settings, why is my DNA information not taken into account during my annual health check-up, where markers such as cholesterol, homocysteine or vitamin D levels are assessed?
I can already tell you that the answer has nothing to do with costs or technical complexity, since today it is possible to analyse specific genetic markers at a similar cost to measuring the blood levels of a particular vitamin.
Probabilities, actionability and managing uncertainty
Our DNA is not a crystal ball that tells us everything that will happen to us in life. In very few cases does a specific genetic variant directly lead to disease. In fact, there are millions of variants in our genome whose impact on overall health we still do not understand, if they have any impact at all.
Genetic diagnosis today is largely reactive. If a patient is suspected to be at risk, either because they show characteristic symptoms or because there is a family history of certain diseases, clinicians look for genetic variants or mutations that could cause or predispose that individual to the suspected condition.
What is more, clinical guidelines do not even recommend analysing variants that are not considered actionable. This means that, even if this information were known, it would not allow changes to prognosis or treatment, nor would it improve patients’ health, wellbeing or quality of life. It is worth remembering that medical practice is guided by an ethical principle that can be summarised as “do no more harm than good”. What sense does it currently make to tell a 30-year-old that they have a high probability of developing a neurodegenerative disease (such as Alzheimer’s) at the age of 70 or 80?
Personalised medicine within the healthcare system
Medical practice, quite rightly, tends to be based on a conservative approach that prioritises objective, present-day data rather than possibilities in a distant future. The technology needed to offer cost-effective genetic screening to the population is already available. But what impact would the large-scale implementation of these techniques have on our healthcare system?
As is often the case, the technological component would be the least significant cost. The major challenge involved in applying genetic analysis techniques lies in managing the uncertainty of the results, adapting generic protocols to personalised ones, and training practising healthcare professionals in new disciplines that do not yet formally exist in our country. This requires a great deal of time and represents a substantial opportunity cost, and, as we know, time is money, and the system cannot be stretched any further.
Treating disease vs. preventing illness
Public healthcare spending in Spain has continued to rise since 1980 and will keep increasing as life expectancy grows. We are treating more diseases, and doing so more effectively, which allows us to live longer, with better quality of life and a level of health that would otherwise not be possible. Or is there another way?
As we unfortunately observed during the COVID-19 pandemic, basing health policies solely on “treating disease” is not sustainable. The only way to ensure the sustainability of healthcare systems is not by “curing more”, but by helping people to “fall ill less”. Could we not apply the same techniques used in personalised medicine to treat disease more effectively in order to prevent those diseases from occurring in the first place?
The answer to this question will be explored in the next article in this series.
