Risk of breast cancer with hormone replacement therapy

Abstract

The age-related rise in breast cancer incidence is steeper prior to menopause. Hormonal changes during menopause are likely to be responsible for the less pronounced increase in risk after menopause. Hormone replacement therapy (HRT) elevates serum levels of estrogens to those of premenopausal women, thus eliminating the relative protection menopause confers. Epidemiologic evidence supports a positive association between HRT use and breast cancer risk that increases with increasing duration of use. This excess risk decreases after HRT cessation. Cell proliferation is the likely mechanism underlying the hormone-induced increase in breast cancer risk. The addition of progestin may increase the rate of cell proliferation beyond that of estrogen alone. Recent epidemiologic evidence indicates a higher breast cancer risk associated with combined estrogen and progestin use than with estrogen alone. Adoption of an HRT regimen should be an individual decision largely based on menopausal symptoms. The risk of osteoporosis and possibly of coronary heart disease may be reduced by HRT use but can also be decreased by lifestyle and risk factor modification. Such measures are not readily available for the prevention of cancer, and the risk–benefit evaluation of HRT use should take this fact into account.