Hormone replacement therapy and breast cancer

There is considerable evidence that the risk of breast cancer is related to ovarian function. However, the effect of postmenopausal hormone replacemen t therapy (HRT) on breast cancer risk continues to be debated in the absenc e of data from randomised controlled trials. Observational studies suggest that HRT probably promotes the growth of pre-existing breast cancers rather than initiating malignant transformation of breast epithelial cells but wi thout exerting an obviously detrimental effect on disease-specific mortalit y. The controversy surrounding HRT and breast cancer has become additionall y more complex as a result of the dilemma faced by clinicians advising wome n rendered oestrogen-deficient by breast cancer therapy. Whilst HRT is curr ently contra-indicated due to theoretical concerns that it will promote dis ease recurrence, its increasing, ad hoc prescription to symptomatic breast cancer patients has not been associated with an increase in disease recurre nce. Large-scale randomised trials of HRT in healthy women and breast cance r survivors are now ongoing but it will be some years before useful clinica l information becomes available. Until then, the limitations and biases imp licit as a result of the design of observational studies must be borne in m ind when interpreting such studies. (C) 2000 Published by Elsevier Science Ireland Ltd. All rights reserved.