Hormone Therapy in Survivors of Breast Cancer

The use of hormone therapy in postmenopausal women with a history of breast cancer is somewhat controversial. The key background issues in this debate are as follows.

First, breast cancer is clearly a hormone-dependent disease. More specifically, it is dependent on the female hormone, estrogen. This means that many breast cancers (specifically, the ones referred to as estrogen receptor or ER positive) have estrogen binders (receptors). Consequently, estrogens can stimulate the growth of these tumors. Men do get breast cancer, but only at 1% the rate of women.

Second, the likelihood of developing breast cancer is related to the duration of estrogen exposure, and particularly to prolonged, unopposed or uninterrupted exposure to estrogens. Accordingly, this relationship between estrogen and breast cancer is seen in data that shows an increased risk of breast cancer in women with an early menarche (onset of menstrual periods), late menopause, late childbearing (first child after age 30), and no childbearing. There is probably a slightly increased risk of breast cancer with the use of hormone therapy in postmenopausal women.