Abstract

Background Menopausal Hormone Therapy (MHT) can alleviate menopausal symptoms but is associated with increased risk of breast cancer (BC). MHT prescription should be preceded by individualised risk/benefit evaluation; however, data outlining the impact of family history alongside different MHT therapeutic approaches are lacking. Aim To quantify the risks associated with MHT use in women with varying BC family histories of i) developing and ii) dying from BC. Design and setting An epidemiological modelling study (UK women). Method We used i) background risks of BC by age and family history, ii) relative risks for BC associated with MHT use, and iii) 10-year BC-specific net mortality rates to model the risk of developing and dying from BC between the ages of 50 and 80 in women with four different BC family history profiles: 'average', 'modest', 'intermediate', and 'strong'. Results For a woman of 'average' family history taking no MHT, the cumulative BC risk (age 50-80) is 9.8%, and the risk of dying from the BC is 1.7%. Five years' exposure to combined-cyclical MHT (age 50-55) increases these risks to 11.0% and 1.8%, respectively. For a woman with a 'strong' family history taking no MHT, the cumulative BC risk is 19.6%, and the risk of dying is 3.2%. With 5 years of MHT (age 50-55), this increases to 22.4% and 3.5%. Conclusion Both family history and MHT are associated with increased risk of BC. Estimates of the risks associated with MHT for women with different family histories can support decision-making around MHT prescription.