Epidemiology of hormone replacement therapy and breast cancer

Abstract

Most epidemiological studies do not show increased risks of breast cancer with use of hormone replacement therapy (HRT), with the exception of a small increase for current users. Duration of HRT use has no effect on the incidence of breast cancer under 5 years, but a 30-50% increase of risk is probably associated with 10-15 years' use. Data on the type and dose of estrogen used in HRT are contradictory. In contrast to endometrial cancer, combined estrogen /progestin regimens of HRT do not seem to provide protection against breast cancer. The prognosis for women who develop breast cancer while receiving HRT is slightly better than in other women with breast cancer, not on HRT at the onset of the disease, and breast cancer mortality is not increased among users of HRT, though the data are difficult to analyze with certainty.

Key Words:

• EPIDEMIOLOGY
• HORMONE REPLACEMENT THERAPY
• BREAST CANCER
• ESTROGEN
• PROGESTIN