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The relative efficacy and tolerability of the aromatase inhibitors anastrozole (Arimidex®) and formestane are assessed in a direct comparative trial in postmenopausal women with advanced breast cancer. Final results are available and reported here only for oestradiol suppression. Patients were randomised to receive either oral anastrozole, 1 mg once daily, or formestane, 250 mg every 2 weeks intramuscularly. In the anastrozole group, mean serum oestradiol levels fell from 32.1 pmol/l at baseline to 6.5 pmol/l at week 1, and similar levels of suppression were maintained over the next 3 weeks. In the formestane group, mean serum oestradiol levels fell from 31.0 pmol/l at baseline to 9.5 pmol/l at the week 1 assessment. In this group, serum oestradiol levels tended to rise by the 2- and 4-week measurements, i.e. immediately before the next injection was due. Based on the 2- and 4-week measurements, the mean falls in oestradiol levels were 79 and 58% in the anastrozole and formestane groups, respectively (p = 0.0001). More effective and consistent suppression of oestradiol was achieved with anastrozole at the therapeutic dose of 1 mg once daily, orally, than with formestane at the standard dose of 250 mg every 2 weeks, intramuscularly. © 1997 S. Karger AG, Basel.

Original publication




Journal article


Oncology (Switzerland)

Publication Date





19 - 22