Aromatase inhibitor.
Trade name Aromasin.
A steroidal aromatase inhibitor of aromatase, unlike anastrozole and letrozole, it destroys the aromatase enzyme.
Binds irreversibly to aromatase causing permanent inactivation of the enzyme even after the drug is cleared from the circulation.
Intergroup Exemestane Study indicated that switching to the aromatase inhibitor after 2-3 years of tamoxifen improves disease free survival in postmenopausal women with breast cancer, even after they stopped treatment.
Intergroup Exemestane Study of 4,742 subjects in a randomized double blind study of 2-3 years of tamoxifen followed by exemestane or continuing tamoxifen for additional 5 years resulted in a relative risk reduction of 32% and absolute benefit in disease free survival of 4.9% for the exemestane patients.
The Intergroup Exemestane study group study the exemestane treated group did not have improved overall survival or substantial difference in toxicity than the tamoxifen group.
MAP.3 trial indicated a reduced risk of first invasive breast cancer by 65% in healthy postmenopausal women who are at risk for breast cancer, reduced breast cancer precursor lesions, did not increase incidents of serious side effects, and is an alternative option for women at risk for breast cancer (Goss P et al).
Impairs bone mineral density.
In a randomized controlled study comparing exemestane to placebo over 2 years in healthy postmenopausal women for breast cancer prevention, there was an average 6.1% reduction in bone mineral density compared to placebo, without changes in height or fracture risk.
In women with hormone receptor positive disease and advanced breast cancer with recurrence within 12 months of adjuvant therapy, everolimus plus exemestane improved median progression free survival 11.5 compared to 4.1 months with placebo plus exemestane (Rugo HS et al).
The TEXT (Tamoxifen and Exemestane Trial) and SOFT (Suppression of Ovarian Function Trial) showed that exemestane plus ovarian function suppression was superior to tamoxifen plus ovarian suppression in preventing recurrence in premenopausal women with hormone sensitive breast cancers (Pagani O et al).
Data suggest that Exemestane is less effective in lobular breast cancer than the two nonsteroidal AI’s anastrozole or letrozole.