Hormone replacement therapy and the breast.

Increasing numbers of women are using hormone replacement therapy (HRT) in their 50s and 60s. Oestrogen alone or oestrogen and progestogen combined given in this age group increase breast density and this has the effect of reducing both the sensitivity and specificity of breast screening in HRT users. HRT significantly increases the risk of developing breast cancer with combinations of oestrogen and progestogens increasing the risk to a greater degree than oestrogen alone. The longer HRT is used the greater the risk with 5 years use being associated with risks of 1.05-1.16 for oestrogen alone and 1.24-1.45 for oestrogen and progestogen combined. No consistent effect of HRT on breast cancer mortality has been demonstrated. Two studies have reported that more than 5 years HRT use is associated with an increased risk of death from breast cancer. A variety of non-oestrogenic agents are available to control menopausal symptoms and these may be of particular value in breast cancer survivors. HRT has been used in breast cancer survivors and although published data are reassuring, none have included sufficient patient numbers to detect small effects of HRT on breast cancer outcome. Prospective randomised trials are underway but are unlikely to include sufficient numbers to exclude a small adverse influence of HRT on breast cancer mortality. Tibolone, a gonadomemetic agent which has been used to control menopausal symptoms, appears to have less direct effects on the breast and is being evaluated as an alternative to oestrogen in breast cancer survivors who develop significant menopausal symptoms resistant to non-hormonal therapies. There is clear evidence that HRT causes breast cancer and the challenge for the physician is to control the menopausal symptoms using HRT or alternatives while at the same time limiting the risks associated with this treatment.