Descriptive analysis of the incidence of thyroid cancer between 1982 and 2012 in France using cancer registries data

The incidence of thyroid cancer has sharply increased in many countries in the past decades. This increase mainly concerns papillary cancers. It has been suggested that changes in diagnostic practices and the effect of risk factors could explain this rise. We present a descriptive analysis in terms of evolution and spatial distribution of the incidence of this cancer in France. Material and method - The incidence analysis is based on data from French cancer registries collected at a district level. A first analysis of incidence involves data covering the whole period 1982-2012. A second analysis describes the spatial distribution of papillary cancer incidence between 2009 and 2012 according to the size of the tumor. The usual epidemiological approaches (direct and indirect standardization) are used in these analyses. Results - The incidence of papillary cancers has sharply increased during the period 1982-2012 with an annual average rate of over 6%. The increase has slowed in the recent period in people aged less than 60 years at the time of diagnosis. The trend differs among the districts covered by cancer registries. There is a strong geographic disparity in the incidence during the period 2009-2012. This disparity concerns all tumor sizes. Three districts report a high incidence (Isere, Gironde and Vendee), and three others show a low incidence (Bas-Rhin, Haut-Rhin and Manche). Conclusion - The incidence of thyroid cancer, especially papillary type cancer, has considerably increased in France. This increase results most probably from the effect of medical practices although other risk factors also seem to be involved, but to a lesser extent. These risk factors have not yet been clearly identified to date so that the geographic disparities observed are difficult to interpret in terms of risk factors. (authors)