Trends in hormone therapy and breast cancer incidence - Results from the german network of cancer registries

Objective: Menopausal hormone therapy (HT) is a proven risk factor for breast cancer. Recent reports presented declining trends in breast cancer incidence, which were attributed to parallel declining trends in HT. Therefore, we analyzed recent data on hormone therapy and breast cancer incidence in Germany. Methods: We performed a population-based survey using breast cancer incidence (from cancer registries) and hormone prescription data (from health insurances) for the time period from 1997 to 2006. Age-standardized rates were calculated and joinpoint regression analyses for trends were performed. Results: Prescription of HT started to decline in 1999; about 2 years later, a parallel decline in breast cancer incidence was observed. HT prescription decreased by 69% up to 2006, and breast cancer incidence by 6.8% for all age groups (2002-2005) and 12.8% in the age group from 50 to 69 years. The reductions in HT prescription and breast cancer incidence were markedly correlated across the federal states in Germany. Conclusion: The recent decline in breast cancer incidence following decreasing HT prescription suggests a causal relationship between the risk of breast cancer and HT in Germany. Even after the 'big HT drop' in Germany, significant differences in HT prescription as well as breast cancer incidence persist at the federal state level. These results should be discussed in a public health context.