The place of exemestane in the treatment of advanced breast cancer in postmenopausal patients

Third generation aromatase inhibitors (AIs) are compounds with proven efficacy in the treatment of early and advanced hormone sensitive breast cancer in postmenopausal women. Due to the distinct mechanism of interaction with aromatase, AIs are divided into steroidal (exemestane) and nonsteroidal (anastrozole, letrozole) inhibitors. AIs inhibit activity of aromatase - an enzyme involved in the conversion of androgens (testosterone, androstenedione) into estrogens (estrone, 17-beta estradiol). In several phase III studies all, third generation" AIs shown to be superior to tamoxifen and progestins in advanced breast cancer. Due to partial non-cross resistance, sequential use of steroidal and nonsteroidal AIs may provide considerable clinical benefit. Since non-steroidal AIs are typically used in first-line treatment, exemestane constitutes a valuable second or third line treatment option. Recently, a combination of exemestane with everolimus, an m-TOR (mammalian target of rapamycine) inhibitor, has been shown to provide clinical benefit in patients progressing on nonsteroidal AIs.