EXOGENOUS ESTROGENS AND BREAST CANCER

Rates of breast cancer at Group Health Cooperative of Puget Sound, Seattle, Washington, a health maintenance organization, remained stable from 1972–1979 in women aged 30–44 years and in women aged 55–64 years, despite the fact that the frequency of use of estrogen-containing drugs has varied substantially. By contrast, rates of breast cancer in women aged 45–54 years appear to have fallen since 1977 in association with a substantial fall in estrogen use in women of this age group. The results are consistent with an etlologic role for current exogenous estrogen in breast cancer in middle-aged women.