Effectiveness of Adjuvant Ovarian Function Suppression in Premenopausal Women With Early Breast Cancer: A Multicenter Cohort Study

Background: Ovarian function suppression (OFS) with tamoxifen or aromatase inhibitors (AIs) improves disease-free survival in premenopausal women with breast cancer, mostly in those at higher risk of recurrence. However, its real-world use and impact remain poorly understood. Patients and Methods: This is a multicenter retrospective cohort study of premenopausal women with stage I to III hormone receptor-positive breast cancer diagnosed from 2006 to 2015 that aimed to look at the uptake and effectiveness of the addition of OFS to backbone endocrine therapy (tamoxifen or AI). To deal with confounding, we used both multivariate modeling and propensity score matching. Results: Of 1717 eligible patients, 17.1% were treated with OFS. There was a substantial increase of use of OFS over time, especially from 2014 onward (16% vs. 25% after 2014), particularly for the combination with AI (0.4% vs. 8% after 2014). In a multivariate model, only younger age and year of diagnosis ≥ 2014 were associated with OFS utilization (both P < .001). With a median follow-up of 38 months (P25-P75, 19.6-66.4 months), patients receiving OFS had a better overall survival than those not receiving OFS (adjusted hazard ratio, 0.44; 95% confidence interval, 0.19-0.96; absolute benefit at 5 years, 2.1% [95.3% vs. 93.2% in those not receiving OFS]). A similar benefit was identified using propensity score matching. Conclusions: In the real-world setting, there was an increase in the use of OFS after 2014. After 2014, one-quarter of premenopausal women received adjuvant OFS, of which more than 30% received it in combination with an AI. In this study, the use of adjuvant OFS was associated with an overall survival benefit.