Will taking Arimidex or other aromatase inhibitors affect breast density?

Aromatase inhibitors block the body’s own production of estrogen and are prescribed for postmenopausal women who have had breast cancer where the tumor cells express receptors for estrogen. One study [1, 2] looked at women who have had breast cancer. When breast density is carefully measured by computer software, women who experienced a decrease in breast density while taking tamoxifen or aromatase inhibitors had a lower risk of recurrence than women who did not experience a decrease in breast density.