Exemestane (
Aromasin) is an orally active steroidal irreversible inactivator of the
aromatase enzyme indicated as an adjuvant treatment in postmenopausal women with
estrogen receptor-positive early-stage
breast cancer following 2-3 years of adjuvant treatment with
tamoxifen, and for the treatment of advanced
breast cancer in postmenopausal women whose disease has progressed following
tamoxifen or other
antiestrogen therapy.
Exemestane is effective for the treatment of postmenopausal women with early-stage or advanced
breast cancer. In early-stage disease, switching to
exemestane for 2-3 years after 2-3 years of adjuvant
tamoxifen treatment was more effective in prolonging disease-free survival than continuing
tamoxifen therapy, although it was not associated with an overall survival benefit, except in those with
estrogen receptor-positive or unknown receptor status disease when nodal status,
hormone replacement therapy (HRT) and
chemotherapy use were adjusted for. Moreover, preliminary data suggest that the efficacy of
exemestane is generally no different to that of
tamoxifen in the primary adjuvant treatment of early-stage
breast cancer, although
exemestane may be better in prolonging the time to distant recurrence. In advanced disease,
exemestane showed equivalent efficacy to
megestrol in patients with disease refractory to
tamoxifen and an efficacy not significantly different from that of
fulvestrant in those refractory to a nonsteroidal
aromatase inhibitor. Available data, some of which are limited, suggest
exemestane is also effective in the first-line hormonal treatment of advanced
breast cancer in postmenopausal women.
Exemestane is generally well tolerated, although the potential
bone fracture risk of the
drug requires further investigation. Results from directly comparative trials indicating the efficacy, tolerability and
bone fracture risk of
exemestane relative to third-generation
aromatase inhibitors and other agents in both early-stage and advanced disease, as well as the optimal sequence of endocrine
therapies, are awaited with interest. In the meantime, switching to
exemestane should be considered in postmenopausal women who have received 2-3 years of adjuvant
tamoxifen treatment for early-stage
breast cancer, and is an emerging treatment option for postmenopausal women with advanced
breast cancer refractory to one or more
antiestrogen therapies.