Background: Breast cancer mortality rates have been decreasing in Spain since 1992. Recent changes in demography, breast cancer therapy, and early detection of breast cancer may change this trend.
Methods: Using breast cancer mortality data from years 1990 to 2009, we sought to predict the changes in the burden of breast cancer mortality during the years 2005–2019 through a Bayesian age-period-cohort model. The net change in the number of breast cancer deaths between the periods of 2015–2019 and 2005–2009 was separated into changes in population demographics and changes in the risk of death from breast cancer.
Results: During the period 1990–2009, breast cancer mortality rates decreased (age-standardized rates per 100,000 women-years 50.6 in 1990–1994 vs. 41.1 in 2005–2009), whereas the number of breast cancer deaths increased (28,149 in 1990–1994; 29,926 in 2005–2009). There was a decrease in the number of cases among women 45–64 years of age (10,942 in 1990–1994; 8,647 in 2005–2009). Changes in population demographics contribute to a total increase of 12.5–12.8% comparing periods 2005–2009 versus 2015–2019, whereas changes in the risk of death from breast cancer contribute to a reduction of 12.9–13.7%. We predict a net decline of 0.1–1.2% in the absolute number of breast cancer deaths comparing these time periods.
Conclusions: The decrease in the risk of death from breast cancer may exceed the projected increase in deaths from growing population size and aging in Spain. These changes may also explain the decrease in the absolute number of breast cancer deaths in Spain since 2005.