Exemestane Tablets

Overview of Exemestane Tablets

Dosage Strength

Commercial (Aromasin®): 25 mg
Commercial (Generic): 25 mg

General Information

A steroidal, irreversible aromatase inhibitor is exemestane. Exemestane is used as adjuvant therapy in postmenopausal women with estrogen-receptor positive early breast cancer and as second-line hormonal therapy in postmenopausal women with metastatic breast cancer. Exemestane’s lack of cross-resistance with tamoxifen, anastrozole, and letrozole—other non-steroidal aromatase inhibitors—means that patients whose breast cancer advances while taking these medications may still respond to exemestane. Compared to anastrozole or letrozole, exemestane results in a more total estrogen blockage. Exemestane had a comparable objective response rate to megestrol in postmenopausal women with advanced breast cancer, but it took much longer for the tumor to develop and for the patients to survive. Exemestane outperformed megestrol in terms of overall response rates and survival in a subset of patients with visceral illness (liver and lung involvement). Exemestane also resulted in less weight gain than megestrol. The Intergroup Exemestane Study (IES), which looked at switching to exemestane after 2–3 years of tamoxifen, found that it offers a better chance of disease-free survival than using tamoxifen continuously for 5 years in early breast cancer. After a median of 30.6 months, the trial was halted due to a significant disease-free survival benefit with exemestane (32 percent relative risk reduction; 4.7 percent absolute risk reduction). 1 The preferred medicine class and standard of care for postmenopausal women with early breast cancer that is hormone-receptor positive is thought to be aromatase inhibitors. All postmenopausal women with early breast cancer that has hormone receptor positivity are advised to take adjuvant aromatase inhibitor therapy, according to the American Society of Clinical Oncology. Options include sequential therapy with 2–3 years or 5 years of tamoxifen followed by 2–3 years or 5 years of an aromatase inhibitor, or 5 years of an aromatase inhibitor. 2 There is no consensus on the ideal therapy and regimen durations. In October 1999, the FDA approved the drug exemestane for the treatment of postmenopausal women with advanced breast cancer who have advanced on tamoxifen therapy. Exemestane was authorized as adjuvant hormonal therapy in postmenopausal patients with early breast cancer that had an estrogen receptor positive in October 2005. Women who have taken tamoxifen for two to three years can move to exemestane to finish out their five years of adjuvant hormone therapy.


1.Coombes RC, Hall E, Gibson LJ, et al. A randomized trial of exemestane after two to three years of tamoxifen therapy in postmenopausal women with primary breast cancer. N Engl J Med 2004;350:1081-92.
2.Winer EP, Hudis C, Burnstein HJ, et al. American Society of Clinical Oncology technology assessment on the use of aromatase inhibitors as adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer: status report 2004. J Clin Oncol 2005;23:619-29.
3.Aromasin (exemestane) tablets package insert. New York, NY: Pfizer Inc; 2018 May
4.Michaud LB. Adjuvant use of aromatase inhibitors in postmenopausal women with breast cancer. Am J Health-Syst Pharm 2005;62:266-73.

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