Menopausal hormone therapy use in relation to breast cancer incidence in 11 European countries

Introduction The use of menopausal hormone therapy (MHT) has decreased in many countries in the past 10 years. This is a consequence of the initial publication of the results of the Women's Health Initiative (WHI) randomized trial of estrogen plus progestin. In various countries, further studies then analyzed the incidence of breast cancer (BC) in relation to changes in MHT use. Some reported a decreased BC incidence following cessation of MHT, but others did not. This may reflect differences in BC incidence, in MHT use or in confounding factors, but also in study methodology. Aim To analyze the changes in BC incidence and MHT use, using the same methodology, in 11 European countries. Materials & method We limited the study to women between the ages of 45 and 69. BC incidence data were provided from cancer registries. MHT sales data were extracted from health sales databases for the years 2003-2013. The association between BC incidence and the rate of MHT use during the past year in Europe was assessed using linear mixed models. Results A drop in MHT sales was consistent in all countries for the whole period of follow-up. This was not the case for BC incidence. We found no evidence of a relation between BC incidence and MHT sales in the past year, except for sales of tibolone. Conclusions The longer observation period did not confirm the results of studies that had a shorter follow-up, except in relation to tibolone. The role of confounding factors needs to be clarified.SCOPUS: ar.j