This commentary article provides an overview of recent clinical research trials involving
anastrozole and its evolving role in the management of
breast cancer. Anti-
aromatase agents inhibit the
cytochrome P-450 component of the
aromatase enzyme complex responsible for the final step of
estrogen biosynthesis in peripheral tissues which are the main source of
estrogen in postmenopausal women.
Anastrozole is a third-generation non-steroidal
aromatase inhibitor. It has been shown to be superior to
megestrol acetate, in terms of survival and adverse effects, as a second-line
therapy in postmenopausal women with
estrogen receptor (ER)- and/or
progesterone receptor (PgR)-positive advanced
breast cancer. Phase III clinical trials have also demonstrated that
anastrozole significantly prolongs the time to tumour progression compared with
tamoxifen as a first-line
therapy for ER- and/or PgR-positive advanced
breast cancer in postmenopausal women. Furthermore, the preliminary results of the
Arimidex,
Tamoxifen, Alone and in Combination (ATAC) study have shown that adjuvant
anastrozole is superior to
tamoxifen in terms of disease-free survival (DFS), non-musculoskeletal adverse effects and prevention of contralateral
breast cancer in postmenopausal women with early, ER-positive
breast cancer. Although longer follow-up is required to assess the long-term effects of
anastrozole on bone mineral density, cognitive function and overall survival, the
drug has been recently approved for adjuvant use in postmenopausal women with early, ER-positive
breast cancer who are unable to tolerate
tamoxifen or at an increased risk of developing
thromboembolism or
endometrial cancer. The potential role of
anastrozole in the neoadjuvant setting, the management of
DCIS, premenopausal
breast cancer and
breast cancer prevention is currently being investigated.