Double-blind, randomised, multicentre endocrine trial comparing two letrozole doses, in postmenopausal breast cancer patients.
Letrozole is an orally competitive aromatase inhibitor. This double-blind, randomised, multicentre trial was carried out to evaluate the endocrine effects of two doses of letrozole, 0.5 mg versus 2.5 mg orally daily, in postmenopausal advanced breast cancer patients progressing after tamoxifen. The pharmacokinetics of letrozole was also assessed. 46 patients entered the trial, 22 on letrozole 0.5 mg and 24 on 2.5 mg. A significant suppression of oestrone and oestradiol levels was achieved by both letrozole doses. Neither letrozole dose induced any changes in cortisol and aldosterone production at rest or after Synacthen stimulation. Androstenedione, testosterone, 17 alpha-OH progesterone, triiodothyronine (T3) thyroxine, (T4) and thyroid-stimulating hormone (TSH) plasma levels did not show any significant changes. Sex hormone binding globulin (SHBG), follicle-stimulating hormone (FSH) and luteinising hormone (LH) levels increased significantly over time. Plasma letrozole concentrations increased until reaching steady-state values after 1 month at the dose of 0.5 mg and after 2 months at 2.5 mg. In conclusion, both letrozole doses suppressed oestrogen levels without affecting adrenal activity.
Bajetta
E
E
Division of Medical Oncology B, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy.
Zilembo
N
N
Dowsett
M
M
Guillevin
L
L
Di Leo
A
A
Celio
L
L
Martinetti
A
A
Marchianò
A
A
Pozzi
P
P
Stani
S
S
Bichisao
E
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001141:Aromatase / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D047072:Aromatase Inhibitors; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D000077289:Letrozole; D008875:Middle Aged; D009570:Nitriles / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics; D017698:Postmenopause; D014230:Triazoles / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics
D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D000077289:Letrozole; D001141:Aromatase