Hormone therapy is used to change the way hormones stimulate cancer growth. These medicines either block the effects hormones have on the cancer cells or block the production of the hormones.

If tests show that the breast cancer cells have estrogen and progesterone receptors (ER/PR-positive), hormone therapy may be used. Tamoxifen and aromatase inhibitors are the most commonly used hormonal therapies. Other hormonal therapies include progestins, such as megestrol (Megace), and antiestrogen, such as fulvestrant.