Hormone replacement therapy and mammographic screening.

The benefits of hormone replacement therapy (HRT) with oestrogen are well known and have led to widespread usage of HRT in post-menopausal women. There is an increased relative risk of breast cancer with prolonged HRT use of 1.7 at worst and this does not warrant more frequent screening. HRT itself makes mammographic screening less effective by adversely affecting both the sensitivity and specificity of screening mammography.A number of large studies have shown a reduction in the sensitivity of screening mammography of between 7% and 21% in current HRT users. This reduction in sensitivity is seen only in women over the age of 50 and is more marked when using single view mammography. The reduction in sensitivity is largely confined to those women who have a dense mammographic background pattern while on HRT. HRT use is also associated with a reduction in specificity of between 12% and almost 50%. This reduction in specificity is mainly found at incident screens. What can be done to minimize the adverse effects of HRT on mammographic screening? The imminent introduction of two views at all screens within the National Health Breast Screening Programme will be helpful. Short-term cessation of HRT use may deter attendance for screening by HRT users and is unproven. Combined oestrogen and progesterone preparations taken continuously appear to be particularly associated with adverse breast screening performance, while tibolone may have little effect on mammographic density. Manipulation of the type of HRT preparations used may allow the adverse effects of HRT on breast screening to be reduced.