Ovarian Function Suppression in Premenopausal Women With Concurrent Endocrine Therapy Use

Not all premenopausal women with breast cancer on antiestrogen therapy and chemical ovarian blockade achieve adequate ovarian suppression. Performed at a single institution, this retrospective study included 131 women receiving combination therapy over a 10-year period. Almost one-third of patients lacked adequate ovarian suppression at least once during treatment, emphasizing the need for serial estradiol monitoring and clinical guidelines. Introduction: Almost 20% of patients receiving ovarian function suppression (OFS) and endocrine therapy (ET) for breast cancer treatment had inadequate OFS within the first year of treatment. Few studies have explored the long-term effectiveness of OFS to maintain estrogen suppression. Patients and Methods: This retrospective, single institution study examined premenopausal women with early-stage breast cancer undergoing treatment with OFS and ET. The primary endpoint was the percentage of patients with inadequate ovarian suppression (estradiol >= 10 pg/mL) during OFS cycle 2 or later. The secondary endpoint was the percentage of patients with inadequate ovarian suppression within the first cycle after OFS initiation. Differences in age, body mass index (BMI), and previous chemotherapy use were summarized via multivariable logistic regression. Results: Of the 131 patients included in the analysis, 35 (26.7%) lacked adequate suppression during OFS cycle 2 or later cycles. Patients with adequate suppression throughout treat-ment were more likely to be older (odds ratio [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). A total of 20 of 83 patients (24.1%) had an inadequately suppressed estradiol level within 35 days of OFS initiation. Conclusion: This "real world" cohort demonstrates that estradiol concentrations above the postmenopausal range of the assay are frequently detected, including more than 1 year after the start of OFS. Additional research is needed to establish estradiol monitoring guidelines and optimal degree of ovarian suppression.