Ovarian steroid hormones and anti-estrogens: Risks for and prevention of cancers of the breast and endometrium in the menopause

Most cellular and organ-specific effects of ovarian steroid hormones (e.g., estrogen and progesterone) are mediated by steroid-hormone receptors. Howe ver, the effects of these hormones can be lost despite the presence of rece ptors. Hormone replacement therapy reduces overall mortality but slightly i ncreases the risk for breast cancer, regardless of the type of replacement therapy. Anti-estrogens such as tamoxifen and raloxifene, alone or in combi nation with steroid hormone replacement, reduce the incidence of breast can cer in women at low risk for the disease. Estrogen monotherapy and tamoxife n increase the incidence of endometrial cancer. Combined hormone replacemen t and raloxifene do not have this effect on the endometrium. Prospective st udies of hormone replacement in patients with a history of breast or endome trial cancer are ongoing. The use of anti-estrogens for reducing the risk o f breast cancer is being addressed in prospective trials with mortality as the primary endpoint. Currently hormone replacement in patients with a hist ory of cancer of the breast or endometrium and anti-estrogens for preventio n of breast cancer should be limited to clinical trials.