A RANDOMIZED COMPARISON OF ESTROGEN SUPPRESSION WITH ANASTROZOLE AND FORMESTANE IN POSTMENOPAUSAL PATIENTS WITH ADVANCED BREAST-CANCER

The relative efficacy and tolerability of the aromatase inhibitors ana strozole (Arimidex(R)) and formestane are assessed in a direct compara tive trial in postmenopausal women with advanced breast cancer. Final results are available and reported here only for oestradiol suppressio n. Patients were randomised to receive either oral anastrozole, 1 mg o nce 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 suppressio n 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 te nded to rise by the 2- and 4-week measurements, i.e. immediately befor e 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 anastrozol e 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.