Estrogen suppression in premenopausal women following 8 weeks of treatment with exemestane and triptorelin versus triptorelin alone

Introduction Luteinizing hormone-releasing hormone (LHRH) agonists (e.g., triptorelin) reduce ovarian estrogen production in premenopausal women with hormone-sensitive breast cancer. Aromatase inhibitors (e.g., exemestane) inhibit extraovarian production of estrogen and may further reduce circulating estrogens when combined with an LHRH agonist. Methods Healthy premenopausal women were randomized to receive 3.75 mg triptorelin (T) on days 1 and 29 with 25 mg exemestane (EX) or matched placebo once daily for 8 weeks, from day 1 to day 56. The primary objective was to evaluate the effect of T ± EX on estradiol (E₂) suppression by comparing the AUC_day36–57 for the 2 treatments. Secondary objectives included evaluation of estrone (E₁), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) suppression; effects of EX on the T-induced gonadotrophin and estrogen flare; pharmacokinetics (PK); and safety. Results Twenty-eight (14 in each arm) were evaluable for efficacy and PK. Mean plasma estrogen levels (AUC_day36–57) were significantly lower for subjects who received T + EX than for subjects who received T alone (20.6 vs. 54.0 pg d/ml [−62%; P < 0.05], and 38.9 vs. 198.0 pg d/ml [−80%; P < 0.01] for E₂ and E₁, respectively). Coadministration of EX did not affect the initial flare or subsequent suppression of LH and FSH following the first dose of T, or the PK of T. Both treatments were well tolerated. Conclusions Coadministration of T and EX resulted in greater estrogen suppression than when T was given alone. These findings could translate into improved clinical outcomes for premenopausal breast cancer patients receiving LHRH agonists.