Hormone replacement therapy and breast cancer.

Hormone-replacement therapy (HRT) has been available for many years, but the important question of its place in development and progression of breast cancer remains controversial; provision of reliable risk estimates has been hampered by a lack of controlled data. Observational evidence suggests that the risk of breast cancer may be increased only if HRT is used long term (ie, for longer than 10 years) and that the risk falls when use ceases. Systematic bias and the lack of adequately powered studies prevent any firm clinical recommendations about the prescription of differing HRT regimens and risk, or the effect of HRT on breast-cancer proliferation and mortality. This review aims to summarise current clinical data, justifying the need for prospective controlled trials in healthy women as well as those at higher risk of breast cancer or with a personal history of the disease.