Ovarian function suppression in premenopausal patients with concurrent endocrine therapy use.

Abstract

6574 Background: The addition of ovarian function suppression (OFS) to endocrine therapy (ET) for premenopausal women with high risk, hormone receptor-positive breast cancer improves disease outcomes. However, in the SOFT-EST study, up to 17% of patients receiving gonadotropin-releasing hormone agonists (GnRHa) did not have appropriate ovarian suppression within the first year of treatment. Few studies have explored the long-term effectiveness of OFS to maintain estrogen suppression. Guidelines for estradiol monitoring during OFS therapy are not clearly defined. Methods: We performed a retrospective, single institution review of all patients who received concurrent GnRHa injections and ET since 2010. Only estradiol concentrations that were assessed during OFS treatment were abstracted from the medical record and included in the analysis. The primary endpoint was the percentage of patients with a non-suppressed estradiol concentration (defined as standard estradiol or high-sensitivity estradiol ≥ 10 pg/ml) identified during OFS cycle 2 ( > 35 days after OFS initiation) and/or later cycles. The secondary endpoint, which included only those patients with estradiol assessment within 35 days of OFS initiation, was the percentage of patients with a non-suppressed estradiol level when measured within the first 35 days after OFS initiation. For both cohorts, differences in age, body mass index (BMI), and previous chemotherapy use were summarized via multivariable logistic regression. Results: 148 patients received concurrent OFS and ET. Patients were excluded because of lack of estradiol assessment during OFS therapy (n = 13) and non-compliance with GnRHa injections (n = 4). The average age and BMI were 43.1 years and 29.1 kg/m2, respectively. 35 of 131 patients (26.7%) had at least one non-suppressed estradiol level during OFS cycle 2 and/or later cycles. The median time to detection of non-suppression was 250 days (range: 53 – 2573 days). Patients whose estradiol concentration remained suppressed throughout treatment with OFS and ET were more likely to be older (OR 1.12 [95% CI 1.05-1.22], p =.02), have a lower BMI (OR 0.88 [95% CI 0.82-0.94], p <.001), and have received chemotherapy (OR 6.30 [95% CI 2.06-20.8], p =.002). For the secondary endpoint, 20 of 83 patients (24.1%) had a non-suppressed estradiol level within 35 days of OFS initiation. Lower BMI was associated with achieving ovarian suppression by 35 days (OR 0.85 [95% CI 0.77-0.93], p <.001); no association was noted for age or chemotherapy. Conclusions: More than one-fourth of patients in this “real world” population had at least one non-suppressed estradiol level during treatment, both the month after the initial OFS dose and at later time points. Patients on OFS, especially those on aromatase inhibitor therapy and those at increased risk of non-suppression, may require frequent and long-term estradiol monitoring during treatment.