Objective: The aim of this study was to assess the impact of the scientific evidence reported by Women's Health Initiative (WHI) trial on hormone therapy (HT) use in a 10-year follow-up retrospective cohort of women participating in a breast cancer screening program.
Methods: Between 1998 and 2007, a retrospective cohort of participants in a population-based breast cancer screening program in the city of Barcelona (Catalonia, Spain) was assessed. The study population consisted of 50,918 women. Trends in current HT use and the annual rate of new users were analyzed by age group.
Results: From 1998, successive annual increases were found in the prevalence levels of HT use in all age groups. In 2002, the prevalence peaked at 11% in 50- to 54-year-olds and at 10.1% in 55- to 59-year-olds, followed by a sudden reversal and a progressive decrease. In 2007, 5 years after the publication of the WHI trial, the HT use decreased by 89.1% in 50- to 54-year-olds, 87.5% in 55- to 59-year-olds, 84.6% in 60- to 64-year-olds, and 66.0% in 65- to 69-year-olds. The percentage of new users also fell substantially after 2002.
Conclusions: HT use decreased during the 5 years after the publication of the WHI. This reduction was especially marked in the first 2 years, when the decrease in new treatments exceeded the number of continuations. In the following 3 years, the decrease was approximately equal in both groups.