[Cancer epidemiology after the Chernobyl accident].

The radioactive fallout from the Chernobyl accident, on 26 April 1986, has caused contamination of very wide areas of the northern hemisphere, in particular in Europe, causing chronic exposure of millions of people to a mixture of external and internal radiation. This paper summarizes the epidemiological studies published to date on the risks of cancer following the Chernobyl accident. An increase in the incidence of thyroid cancer observed among those exposed in childhood and adolescence in the most contaminated territories of Belarus, Russia and Ukraine is at present the only scientifically demonstrated radiation-related increase in cancer incidence. This observation provided important information on the risk of thyroid cancer related to 131I and on factors, such as iodine deficiency and stable iodine supplementation, which can modify this risk. The reports on increases in the incidence of other types of cancer are difficult to interpret because of methodological limitations. As the majority of these studies cover a relatively short time period, it is not possible to fully evaluate the radiological impact of the accident, and it is premature to draw conclusions on the risk of cancers other than that of thyroid. Predictions, based on the experience of other populations exposed to ionizing radiation, suggest that a substantial number of cancers could occur in Europe, especially in the most contaminated areas. Well-focused studies could verify these predictions, in particular with regard to the risks of leukaemia among liquidators and breast cancer among young women in the most contaminated areas.