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

Despite the wide use of a three-month gonadotropin-releasing hormone agonist (3M GnRHa) for ovarian function suppression (OFS) in premenopausal breast cancer patients, it remains unclear whether it is as effective and safe as a one-month GnRHa regimen (1M GnRHa) when combined with selective estrogen receptor modulators (SERMs) or aromatase inhibitors (AIs), especially in younger patients. This retrospective cohort study included 1109 premenopausal hormone receptor-positive (HR+) breast cancer patients treated with GnRHa plus SERM or AI. The estradiol (E2) inhibition rate within 1-24 months after treatment with 1M or 3M GnRHa in cohorts and different subgroups was analyzed. 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 1M and 3M groups achieved >90% E2 inhibition within 24 months (94.53% vs 92.84%, 95% CI (-4.78%, 1.41%)), confirming the non-inferiority of 3M GnRHa. Both 1M and 3M GnRHa rapidly and consistently reduced E2 levels. 60 (6.3%) patients experienced incomplete ovarian function suppression (iOFS), with similar rates in the 1M and 3M groups (5.5% vs 7.2%). iOFS mainly occurred within the first 12 months, with age .05). The OFS with 3M GnRHa was not inferior to that with 1M GnRHa, regardless of age or combination with a SERM or an AI.