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.

Third, one of the most effective strategies in the management of estrogen receptor (ER) positive breast cancer is the use of anti-estrogens, such as tamoxifen (Nolvadex), or aromatase inhibitors, such as anastrozole (Arimidex). The tamoxifen interferes with the attachment (binding) of estrogen to its receptor in the breast. The anastrozole blocks the production of estrogen in non-ovarian tissues, which become the principal source of estrogen in post-menopausal women. These anti-estrogenic agents have been clearly demonstrated to be effective in the treatment of metastatic (spread beyond the breasts) breast cancer and as additional (adjuvant) treatment of primary (initial) breast cancer.