The aim of this study was to compare the efficacy and tolerability of the new
aromatase inhibitor '
ARIMIDEX' (
anastrozole) with
megestrol acetate in the treatment of advanced
breast cancer in postmenopausal women.
Anastrozole is a new potent and highly selective non-steroidal
aromatase inhibitor. We conducted a prospective randomised trial comparing two doses of
anastrozole (1 and 10 mg orally once daily) with
megestrol acetate (40 mg orally four times daily) in postmenopausal patients with advanced
breast cancer who progressed after prior
tamoxifen therapy. All patients were analysed for efficacy as randomised (intention to treat) and for tolerability as per treatment received. Of the 378 patients who entered the study, 135 were randomised to
anastrozole 1 mg, 118 to
anastrozole 10 mg, and 125 patients to
megestrol acetate. After a median follow-up of 192 days, response rate which included complete response, partial response and patients who had disease stabilisation for 6 months or more was 34% for
anastrozole 1 mg, 33.9% for
anastrozole 10 mg and 32.8% for
megestrol acetate. There were no statistically significant differences between either dose of
anastrozole and
megestrol acetate in terms of objective response rate, time to objective progression of disease or
time to treatment failure. The three treatments were generally well tolerated, but more patients on
megestrol acetate reported
weight gain, oedema and dyspnoea as adverse events while more patients on
anastrozole reported gastro-intestinal disorders, usually in the form of mild transient
nausea. Patients on
anastrozole did not report higher incidences of oestrogen
withdrawal symptoms.
Anastrozole is an effective and well tolerated treatment for postmenopausal patients with advanced
breast cancer. The higher 10 mg dose did not result in additional clinical benefit, but was well tolerated reflecting the good therapeutic margin with
anastrozole. Based on this data,
anastrozole 1 mg should be the recommended therapeutic dose.