Different dosage forms of GnRHa with endocrine therapy in premenopausal hormone Receptor-Positive breast cancer

Abstract Background Despite the wide use of a 3-month gonadotropin-releasing hormone (GnRH) agonist for ovarian function suppression in premenopausal breast cancer patients, it remains unclear whether it is as effective and safe as a 1-month GnRH agonist regimen when combined with selective estrogen receptor modulators or aromatase inhibitors, especially in younger patients. Methods This retrospective cohort study included 1109 premenopausal hormone receptor–positive breast cancer patients treated with GnRH agonist plus selective estrogen receptor modulator or aromatase inhibitor. The estradiol (E2) inhibition rate within 1-24 months after treatment with 1-month or 3-month GnRH agonist in cohorts and different subgroups was analyzed. Results Following 1:1 propensity score matching, 950 patients with a mean age of 39 years and a median follow-up of 46 months were included. Both the 1-month and 3-month groups achieved more than 90% E2 inhibition within 24 months (94.53% vs 92.84%, with a 95% confidence interval for the difference ranging from −4.78% to 1.41%), confirming the noninferiority of 3-month GnRH agonist. Both 1-month and 3-month GnRH agonist rapidly and consistently reduced E2 levels. Of the patients, 60 (6.3%) experienced incomplete ovarian function suppression, with similar rates in the 1-month and 3-month groups (5.5% vs 7.2%). Incomplete ovarian function suppression mainly occurred within the first 12 months, with age younger than 40 years and no prior chemotherapy being the risk factors. Similar disease-free survival and overall survival were found in the 1-month and 3-month groups and in patients with complete and incomplete ovarian function suppression (P > .05). Conclusions The ovarian function suppression with 3-month GnRH agonist was not inferior to that with 1-month GnRH agonist, regardless of age or combination with a selective estrogen receptor modulator or an aromatase inhibitor.