Interview with António Parreira, Clinical Director of the Champalimaud Clinical Centre
Has there been an increase in the number of cancer cases? What is the reason for this?
We know that there has indeed been an increase. The question is to try to understand how we can, not only understand this phenomenon, but also, somehow, minimise its effects.
This phenomenon has to do with ageing. The development of cancers is one of the very direct consequences of ageing.
The reality is striking: less than 5% of all cancers occur in childhood – that is, under the age of 12, of 15. And 90% of the cancers that afflict humans occur after the age of 50.
When we look at the incidence curves for breast cancer, lung cancer, bowel cancer, stomach cancer, haematological cancers, uterine cancers, ovarian cancers and so on, what we see is that the number of cases per 100,000 people increases with age. It only starts to decline at the age of 90, 95.
Exceptions to this rule are some cases of breast cancer that occur in younger women, probably due to genetic defects that increase risk in younger people. It is also well known that certain haematological cancers occur in younger people.
However, people are often unaware of this. They know that cancer is more common in older people, but they don't have a clear understanding of what that means, or why it happens. And this is not theoretical, it is a fact, and today, because of that, many research centres and scientists are studying the cancer-ageing relationship.
Why does cancer increase with age?
It happens for reasons of a biological nature and there is now a relatively extensive bibliography on the subject.
As we have known for many years, cancer is a disease caused by mutations in the cells of our body. The accumulated mutations create conditions in which the regulation of cell function is insufficient to the point where cells can begin to proliferate and grow without respecting the harmony of the organism. They become like aliens, capable of destroying the tissues around them, and sometimes at a distance – and eventually leading to the organism’s – the person’s – death.
At younger ages, in the vast majority of cases, these defects are fortunately repaired by DNA repair systems: intrinsic cellular systems, defence mechanisms that depend on the cells surrounding the cells in which these abnormalities occur – the so-called "tumour microenvironment" –, which have to do essentially with cells that participate in immune response processes.
One of the interesting things that needs to be mentioned is that, in fact, the reason why we don't generally get cancer at younger ages is because, at that stage of life, the set of defence mechanisms against the emergence of cancer is particularly robust.
How can this age-related robustness be explained?
The fact that these mechanisms are so extremely robust in young people probably has to do with the conservation of the species from an evolutionary point of view. In other words, with the need to preserve the normality of our bodies during our reproductive life so that we are able to procreate and perpetuate our species.
Thus, some argue that the reason these mechanisms lose their robustness and effectiveness after the age of 50 or 60 is because we are no longer of childbearing age. There is no longer the selective pressure of Darwinian evolution to preserve organisms. They have already procreated, they are no longer needed.
Do you agree with this theory?
It’s just one possible explanation. But it is a fact that the increase in cancer with age has to do with phenomena underlying our ageing processes. We know that our body's repair mechanisms become less effective after the first decades of life. The very structure of tissues becomes more fragile.
And on top of that, we often add environmental factors, lifestyle habits, which will do even more damage, because they will contribute to the increased likelihood of the occurrence of mutations capable of leading to anomalies that are at the root of cancer.
With people living longer and an ageing population, could cancer become the leading cause of death in rich countries?
Yes. Currently, the leading cause of death is still cardiovascular disease. But that may soon cease to be the case and we are probably not many years away from having cancer as the leading cause of death.
Can we fight the ageing of the body to prevent this from happening?
We already have ways to fight certain aspects of ageing. We can reduce its negative repercussions. There are many examples of this. When our eyes are clouded by cataracts, an ophthalmologist can remove the now-opaque lens of the eye and replace it with an artificial lens.
When we have a joint that has almost been destroyed by ageing, an orthopaedic surgeon can replace our knee or hip so that we can continue to have quality of life. The examples are countless.
We can indeed counteract the effects of ageing, but from a biological point of view, that's not enough. At least not yet. There is a biological reality that we do not know how to control, nor do we have the capacity to alter it.
If we can't change the biology, what can we do to counteract the increase in the likelihood, over time, of having cancer?
We can lead a healthy life so that our bodies are more resistant to the onset of the disease: we need to lead an active life, exercise regularly, avoid overeating, avoid environmental risks – at least those we can, such as smoking and, as much as possible, air pollution, etc. And avoid obesity, which is an undisputed major risk factor for several types of cancer, not only because of obesity itself, but also because of obesity-related inflammation.
Like many other predators in nature, we evolved in a state of permanent hunger, of permanent lack of food. We were – and still are – biologically “programmed” to be hungry all the time. And, from the moment food became easy to access, because you just have to open the fridge door and help yourself, we were doomed to have an increasing obesity rate in the most economically developed societies.
The chance of any one of us developing cancer today, over our lifetime, is one in two or three. It's not a rare thing. We all know we might get it. And the longer we live, I repeat, the more likely we are to get cancer.
We can also do surveillance.
Yes, surveillance is indeed important, as it gives us opportunities for the very early diagnosis of cancer. And early diagnosis can mean, in many circumstances, that we have a (very small) temporal chance to succeed with a curative treatment.
At a very early stage, the surgeon is able to extract the cancer completely. Patients can be clinically cured and sometimes truly cured. This is true for lung cancer, but also for stomach and breast, prostate and ovarian cancers – even for pancreatic cancer, which is a very lethal cancer.
Nowadays, we can detect the early forms of certain cancers, for example breast cancer, and there are screening programmes that allow us to detect early symptoms, through systematic examinations, even before the cancer appears. The same is true for stomach, colon and even lung tumours, although the latter are more difficult to detect in their early stages.
With colon cancer, in particular, even if it is detected already at the cancerous stage, but that the tumour is very localised, can be completely removed.
Concerning the prostate, it's not so easy. Nevertheless, we have a relatively robust blood indicator for prostate cancer: PSA. If a man, from the age of 45, 50, is monitored by measuring his PSA, this can allow, in the vast majority of cases, to detect the onset of cancer. And because this cancer is usually relatively slow-growing, the chance of finding the window of effective treatment is greater than with faster-growing cancers.
Today, cancer is not a death sentence.
Can we prevent cancer by assessing our risk of getting cancer?
In people with a family history of cancer, in particular, one way to try to prevent the disease is to have their individual risk assessed. This is another tool to optimise surveillance strategies.
If we know that a person has a hereditary alteration in certain genes that increases the likelihood of that person developing a certain type of cancer – for example, in the case of breast cancer, mutations in the BRAC1 and BRAC2 genes –, this justifies earlier surveillance and even, in some cases, removal of the organ before cancer occurs.
[At the Champalimaud Foundation, there is an oncological risk assessment and management programme, the Oncorrisk programme – see here for more details: https://fchampalimaud.org/pt-pt/clinical_programs/programa-de-oncorrisco]
Do you think that people in Portugal realise the importance of doing cancer prevention?
In Portugal, the population knows and is aware that prevention is necessary. I think that, in this respect, the Portuguese population has shown a great degree of maturity and that the screening programmes that have been carried out have met with quite high levels of public adherence.
The Portuguese population has, I would say, a strongly positive attitude towards cancer prevention.
Interview by Ana Gerschenfeld, Health & Science Writer of the Champalimaud Foundation.