(Paper originally published in Le Monde on April 2, 2008)

Environmental effects are underestimated according to Dr. Annie Sasco, Epidemiologist at INSERM

After spending over twenty years at the International Agency for Research on Cancer (IARC) Dr. Annie Sasco, is now head of the research team of the Unit of Epidemiology for cancer prevention (INSERM Unit 897 – Bordeaux).

On the 18th of February, the National Academy of Medicine reported a decrease in the number of breast cancer cases since 2005, a result that it ascribes to a decrease in the use of hormone-replacement therapy (HRT). Scientific studies reporting side effects of HRTs that date back to the early 2000s. Can we reach this kind of conclusion in such short notice regarding the impact of a decreased use of these therapies?

Hormonal products can have two types of mechanisms of action: either as carcinogens, by inducing DNA mutations; or as efficient growth factors, thereby promoting cell growth, in particular cancer cells.
Since we are considering a growth promotion effect in a relatively short term, this can explain how the interruption of HRT among women who are in an age range where they are prone to have a certain number of cancer cells in their organisms (which does not imply that all of them will eventually develop into cancer) can result in a fast decrease in the number of cancer cases.
In some individuals, cancer cells can lie dormant, kept in check by the immune system. But these cells can be reactivated if stimulated by growth factors. This doesn’t mean that HRT is solely responsible in the development of cancer. There are other factors all well, but HRT can play a role in the occurrence of breast cancer.

The Academy seems poised to go ahead with chemoprevention in women who are – owing to genetic susceptibility - exposed to a higher risk of developing breast cancer. What is your opinion?

I think that we would be well advised to wait. In any case, this cannot be the answer for the whole population. Increased recourse to medications is not the only answer. We are actually being misled: people who are not yet ill are being treated in order to prevent the development of diseases. This is the case for many ailments (hypertension, high cholesterol, etc). The problem is that we are not even sure that we can actually prevent the diseases from occurring. Still, medications, that may be efficient, but are at the same time aggressive with potential side effects, are being largely prescribed. Even in the case where medications considered to be safe, such as vitamins (beta carotene, alpha-tocopherol, etc,), have been prescribed to prevent lung cancer among smokers, this has not worked.
People developing lung cancer have been found to have lower blood vitamin levels. Thus, the idea behind vitamin supplementation in this case. However a preliminary study carried out in Finland fifteen years ago showed that those subjects given vitamin supplementation actually developed more lung cancer cases as compared to those who received nothing. It is never neutral to modify nutrient supplies of people through chemical means. The same applies to food products. It would be naïve to consider that one could actually compound all the benefits of a class of food products into a few chemical pills. That would equate to look for simple solutions just because it is easier to prescribe than to forbid.

How can we improve cancer prevention?

It is perfectly sensible to advise people not to smoke, to drink less, to have a healthy diet, preferably without pesticide residues or pollutants, and to exercise regularly. But there are also other factors which we cannot control at our individual level: the air we breathe, the water we drink, the environment in which we live, or exposure to electromagnetic fields. More drastic measures should be taken, especially regarding the use of pesticides. Nowadays, when we are having a normal meal in France, we are exposed to the residues of 21 pesticide products. While we should as much as possible try to eradicate all compounds that are known or strongly suspected to be carcinogenic for the human being from our lifestyle and environment, unfortunately it isn’t always up to us. There are economic interests at stake. Each one of us can exert an influence to curb the political decisions on such matters.

Recent studies have shown that the weight of the environment (water, air, food supplies) in the occurrence of cancers is extremely small, less than 1% …

The available figures actually reflect what has been happening over the past thirty years. Forty years before now, we were much less exposed to pesticides or magnetic fields in our environment. Mobile phones or wi-fi technology did not yet exist. Cancer is a side-effect that occurs in the long run. It may take up to twenty or forty years for a cancer to develop. For instance, we are just beginning to apprehend the potential side effects of mobile phones. We are surrounded by an environment of magnetic waves. Whether be it food products, ionizing radiations, electromagnetic fields, dioxins or even some cosmetic products, can we afford to wait till we are absolutely sure about their potential consequences? Should we not instead take a precautionary stance in view of the data already available from animal studies and also from some studies carried out on the human being which are not really reassuring? Regarding cosmetic products, one must be aware that the price tag certainly does not offer any kind of guarantee in quality difference.

All this means that there would be a lot for us to look out for…

I do not want to scare the population. But these subjects must be addressed. If the increased number of cancer cases can be related partially to our ageing population, and also to better screening (as in the case of prostate cancer), they certainly cannot account for all the cases. In reference to the speech made by Nicolas Sarkozy at the Qinghua University of Beijing on the 27th of November: “Public opinion demands that we work together to stop the scandal of cancers in relation with the pollution of our environment”, I certainly abide by this statement.

Document translated from French into English by Roland Ah-Song and edited by Annie J. Sasco and Aimée Ward in Bordeaux, June 27, 2008.