[Decline in breast cancer incidence in 2005 and 2006 in France: a paradoxical trend].

The objective of this paper is to measure breast cancer incidence rates between 2000 and 2006, and to analyse during this period the changes in mammographic screening and in the use of hormone-replacement therapy (HRT). Incidence rates were calculated from the new cases of breast cancers among affiliates of the general schema of the national health fund who received first time approval for their long-term disorder. We obtained the trends in HRT use and in mammographic screening from the database of the health fund and from the National Institute for Public Health Surveillance. Between 2000 and 2004, the increase in the annual age adjusted incidence of breast cancer was 2.1 %. Decline in breast cancer incidence was 4.3 % between 2004 and 2005, and 3 % between 2005 and 2006. During this period, the decrease was evident only among women who were 50 years of age or older: the decline was 6 % between 2004 and 2005 and 5.3 % between 2005 and 2006. Between 2000 and 2006, the annual rates of HRT use declined by 62 % and organized screening mammography increased by 335 %. The observation of a decline in breast cancer incidence during the implementation of a screening programme is a paradox. The concomitant and dramatic reduction in the use of HRT is the only major environmental change to explain this trend.