Cancers and environmental exposure: a concerted research effort
The news has been added to your library
News of 15/12/2011
15 December 2011
On 12 December, ANSES, INCa (1) and the AVIESAN (2) alliance invited close to 400 researchers, health professionals and representatives of official institutions and associations to review the current state of knowledge on the relationship between environmental exposure and cancer.
The aim of this international symposium, held in Paris as part of France's Cancer Plan 2009-2013 and the National Environment and Health Action Plan for 2009-2013, was to present recent studies and methodologies that attempt to improve our understanding of the relationship between cancer and the environment and thus help determine the priorities for research in this field.
In 2008, the number of new cases of cancer in the European Union is estimated to have been about 2.4 million, affecting 1.3 million (54%) men and 1.1 million (46%) women.
In 2011, the number of new cases of cancer in France is estimated at 365,000. The most frequent are prostate cancers in men (71,000 cases) and breast cancers in women (53,000 cases). These are followed in men by lung cancers (27,500 cases) and colorectal cancers (21,500 cases) and in women by colorectal cancers (19,000 cases) and lung cancers (12,000 cases).
The overall incidence of all kinds of cancers is on the increase, while mortality is declining. The reduced mortality in France can largely be attributed to improved early screening and better treatment of those diagnosed. The increased incidence of cancers is largely due to the fact that the population is living longer and to improved identification of cancers already present by screening, which is becoming more socially acceptable. However, these two factors alone cannot explain this increase.
The growing incidence of cancer can be observed throughout the world and the number of new cases is increasing significantly, especially in developing countries.
Endogenous causes (involving genetic alteration) account for only 5 to 10% of cases. The other 90 to 95% are related to exogenous causes, meaning the environment in the broadest sense. These include lifestyle choices (smoking, alcohol consumption, sedentarity, dietary habits, exposure to solar radiation, etc.), exposure to natural environmental factors (e.g. radon), and chemical, physical and infectious agents in the general and occupational environment. Both socio-economic and geographical conditions (when these are unfavourable), are also risk factors.
The participants were there to learn more about the links between the environment in the broadest sense and cancer. The role of some environmental factors, such as asbestos, arsenic, emissions from coke ovens, tobacco smoke and human papillomavirus (HPV), has been clearly established.
However, there are several chemical and physical agents with suspected or possible carcinogenic effects that have not yet been confirmed. There are methodological difficulties involved in demonstrating the potential risk: exposure at low doses, which is therefore difficult to quantify, very long latency periods between exposure and the onset of disease, etc. Estimating the combined exposures to several chemical products (cocktail effects) and the corresponding risks is, furthermore, a considerable scientific challenge.
To show any potential risk to humans would require epidemiological studies with very large cohorts and assessment of the related types of exposure.
Several of the studies presented during the symposium illustrated the difficulty of quantitative assessment of exposure. It is consequently very difficult to understand the links between the numerous agents in the environment and the various cancers. The principal studies undertaken on large population groups in recent decades have provided answers for certain environmental factors (exposure to ionizing radiation during childhood, night work, radon, etc.). Even so, in the current state of knowledge, the growing incidence of the most frequent cancers (principally breast, prostate and colorectal) remains partially unexplained.
The symposium highlighted the need to harmonise methods for evaluating exposure so as to facilitate comparison of the results of epidemiological studies. It also showed the need for more research into biomarkers and their mechanisms of action in order to improve the way we measure exposure. Participants also learned about progress in genomics and proteomics, which should lead to the availability of biomarkers for exposure to substances or for early effects. In addition, speakers emphasised the importance of considering vulnerability and critical periods for exposure (the prenatal period, etc.).
The audience was reminded that for knowledge to advance a multidisciplinary approach, bringing together scientists from several fields: biologists, chemists, epidemiologists, exposure specialists, geneticists, physicians, toxicologists, etc., would be required.
The participating scientists acknowledged the work already underway, but agreed that it was necessary to continue to find ways of further evaluating and mitigating exposure today, in order to prevent the onset of cancers tomorrow.
17 research projects on different cancers
17 research projects on different cancers, for a total of more than 2 million euros, have been funded in the framework of the ANSES research programmes into health and the environment, with which INCa and ITMO (AVIESAN's Cancer Unit) have been associated since 2010.