Endocrine changes with the aromatase inhibitor fadrozole hydrochloride in breast cancer.
Fadrozole hydrochloride is a potent aromatase inhibitor with proven clinical effectiveness. However, its optimal dose and its effects on serum aldosterone levels/electrolyte balance have been disputed. To resolve these issues, a double-blind randomised endocrine study of three doses of fadrozole hydrochloride [0.5 mg twice daily (bd); 1.0 mg bd; 2.0 mg bd] was conducted in 80 (68 evaluable) postmenopausal patients with advanced breast cancer over a period of 3 months. There were substantial falls in the serum levels of oestradiol, oestrone and oestrone sulphate. For oestrone only, there was a significant effect of dose (on-treatment means: 0.5 mg, 38.0 pmol/l; 1.0 mg, 25.0 pmol/l; 2.0 mg, 23.9 pmol/l). All oestrogens showed a similar pattern in relation to time, with the 3-month mean being higher than those at 1 and 2 months, and this was significant for oestradiol (P = 0.012). There was an indication that complete suppression of oestradiol and oestrone was not maintained throughout the 12-h dosing period, but the data and its interpretation are complicated by a minor diurnal rhythm in these parameters. There were significant increases in 17-hydroxyprogesterone and androstenedione which may be due to a block of 11 beta-hydroxylase. There was a statistically non-significant fall in aldosterone levels (P = 0.06) during treatment (median pretreatment, 446 pmol/l; median decrease, 125 pmol/l). However, the concurrent significant fall in the plasma sodium: potassium ratio indicated that changes in aldosterone secretion did occur. None of these effects on adrenal pathways was of a degree which is likely to have clinically relevant consequences. It is concluded that fadrozole hydrochloride achieves near maximal suppression of oestrogens at 1 mg bd, and that its effects on aldosterone synthesis are unlikely to be of clinical significance.
Dowsett
M
M
Royal Marsden Hospital, Dept of Biochemistry, London, U.K.
Smithers
D
D
Moore
J
J
Trunet
P F
PF
Coombes
R C
RC
Powles
T J
TJ
Rubens
R
R
Smith
I E
IE
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D047072:Aromatase Inhibitors; D001943:Breast Neoplasms / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004958:Estradiol / Q000097:blood; D004967:Estrogens / Q000097:blood*; D004970:Estrone / Q000031:analogs & derivatives / Q000097:blood; D017316:Fadrozole / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009376:Neoplasms, Hormone-Dependent / Q000097:blood*; D017698:Postmenopause / Q000097:blood
D047072:Aromatase Inhibitors; D004967:Estrogens; D004970:Estrone; D004958:Estradiol; D017316:Fadrozole; C017296:estrone sulfate