Measuring Ovarian Escape in Premenopausal Estrogen Receptor-Positive Breast Cancer Patients on Ovarian Suppression Therapy

Purpose: This study evaluated the proportion of premenopausal women who experience persistent ovarian escape (OE) while receiving ovarian suppression (OS) therapy for estrogen receptor-positive (ER+) breast cancer treatment. The study also examined clinical factors that may predispose to higher risk of persistent OE. Materials and Methods: This was a retrospective, “real-world” study to evaluate premenopausal women receiving adjuvant endocrine OS therapy. The primary objective was to measure the percentage of persistent OE within the first 3 months of OS injections (using either leuprolide or goserelin). The secondary objective was to associate baseline clinical data (age, body mass index [BMI], and previous chemotherapy) with the probability of OE. Results: Of the 46 patients included in this analysis, 11 (23.9%) women did not achieve OS within 3 months. Three women (6.5%) remained in OE at 12 months. Older age (odds ratio, 0.86; confidence interval, 0.76–0.98, p =.024) was associated with lower chance of developing OE. BMI, previous chemotherapy, and drug used (tamoxifen versus aromatase inhibitor) did not correlate with the likelihood of OE in this patient cohort. Conclusion: Among the premenopausal women who did not attain complete ovarian suppression, young age was a significant risk factor for likelihood of OE. Although the clinical relevance of this finding is not yet known, it should prompt further studies to determine whether inadequate OS is associated with higher recurrence risk for patients with ER+ breast cancer. Implications for Practice: Because up to a quarter of premenopausal women do not attain adequate ovarian suppression within the first 3 months of gonadotropin-releasing hormone (GnRH) agonist therapy, bloodwork should be checked to ascertain hormone levels prior to starting aromatase inhibitor therapy, and at regular intervals, for these women.