RESUMO
BACKGROUND: A recent decline in breast cancer incidence rates has been reported in the United States and in Europe. This decrease has been partly attributed to the reduced use of hormone replacement therapy (HRT). No study in Europe has detailed recent breast cancer incidence trends both by hormonal receptor status and mode of detection at an individual level. METHODS: We examined trends in breast cancer incidence rates in the French administrative area of Loire-Atlantique between 1991 and 2007, by age, mode of detection, histological subtype, estrogen/progesterone receptor (ER/PR) status and grade. Annual age-standardized breast cancer incidence rates were estimated using the Loire-Atlantique and Vendée Cancer Registry data. Annual percentage changes (APCs) were estimated using an age-adjusted Poisson regression model. RESULTS: Incidence rates of breast cancer increased 3.5% per year in 1991-2003, dropped -4.3% per year in 2003-2006 and increased in 2007 (9.1%). Stratified analyses by age groups showed that the decrease concerned predominantly women aged 50-64 years, whereas an increasing proportion of cancers detected by organized screening was observed in this age group. Among these women, the decline of incidence particularly concerned positive estrogen and progesterone receptor tumors, lobular subtype tumors, and low-grade tumors. CONCLUSION: The drop in breast cancer incidence rates observed between 2003 and 2006 in women 50-64 years old was greater for ER+PR+ tumors. During the same period, the incidence of breast cancers diagnosed by organized screening increased. These patterns appear consistent with an impact of the reduced use of HRT.