Hows an aromatase inhibitor used for breast cancer?

It is an anti-: Estrogen used in women after menopause, with tumors that have an estrogen receptor. It is not useful if eh ovaries are generating scads of estrogen. And tumors without er do not respond to estrogen maneuvers. It also may be useful as a preventive in older women with in situ cancers, but tamoxifen is standard.

Hormonal therapy: Aromatase inhibitors are a form of hormonal therapy for post menopausal patients. They are effective only in er+ cases. They block the conversion of other hormones to estrogen via the enzyme aromatase. In premenopausal patients they actually stimulate the ovaries to increase estrogen production. Hormonal therapy is systemic treatment, reduces local recurrence, and reduces risk of 2nd primaries.