Hormone replacement and cancer.

The increasing extended use of noncontraceptive oestrogen by postmenopausal women, intended to prevent other conditions, may at the same time increase their risk of reproductive cancer. The risk of endometrial cancer triples after only a few years of unopposed oestrogen, persists for many years after oestrogen has been discontinued, and appears to be preventable by the addition of a progestin. The effect of replacement hormones on the risk of breast or ovarian cancer is unknown. Most studies suggest a small but significant increased risk of breast cancer after long-term use. Awareness of the known and uncertain cancer risks should be included in decisions to use replacement hormones.