Abstract PS3-07-08: Sustained Ovarian Function Suppression with Triptorelin in Premenopausal HR+ HER2− Breast Cancer: Results from the Second Interim Analysis of the ROSE Study

Abstract Background: Ovarian function suppression (OFS) is a cornerstone in the adjuvant treatment of premenopausal women with hormone receptor-positive (HR+), HER2-negative early breast cancer (EBC). Triptorelin is commonly used in this setting, but real-world evidence on its effectiveness across various treatment combinations remains limited. Methods: The ROSE study (NCT05377684) is a multicenter, observational trial designed to assess quality of life (QoL) as its primary endpoint in premenopausal women with HR+ HER2− EBC treated with triptorelin as OFS plus oral endocrine therapy. Chemotherapy was administered based on relapse risk factors and multidisciplinary discussion. Enrollment of total population (n = 451) was completed as of December 2024. This second interim analysis, which included the first 103 patients who completed the follow-up as per protocol, focuses on a secondary endpoint: the evaluation of hormonal suppression over time. Premenopausal patients ≥18 years with stage I-IIIA HR+ HER2− EBC were eligible. Patients received adjuvant endocrine therapy (tamoxifen or aromatase inhibitors [AI]) plus triptorelin (1- or 3-month formulation), started either concurrently or sequentially with chemotherapy. Results: This analysis includes 103 participants who completed ≥2 hormone assessments (estradiol [E2], estrone [E1], FSH) and had 18 months of follow-up. OFS was defined as E2 <30 pg/mL, according to average values collected in Italian centers as per protocol. Results were stratified by treatment combinations and chemotherapy status. The cohort had a mean age of 46.2 years (SD: 4.9); 17.5% received chemotherapy with almost half of them received concomitant triptorelin, and 9.7% received abemaciclib in addition to endocrine therapy. Most patients received AIs (82.5%) and 1-month triptorelin (88.3%). At 6, 12, and 18 months, OFS (E2 <30 pg/mL) was achieved in 84.2%, 91.5% and 93.0%, respectively. Hormone levels showed a sustained suppression over time across all treatment subgroups. Median E2 levels dropped markedly from the first triptorelin injection to 6 months [median: 12.50 (Q1:6.70, Q3: 23.00)] and remained consistently low at 12 [median: 12.16 (Q1: 5.00, Q3: 23.00)] and 18 months [median: 13.95 (Q1: 5.00, Q3: 23.00)] FSH levels rose accordingly, confirming suppression. Among patients (9.7%) receiving triptorelin + AI + abemaciclib, hormonal suppression seemed comparable to that observed in other AI-based combinations (71.8%). The average duration of triptorelin exposure was similar across all subgroups, with a mean of 79.59 (SD: 6.11) weeks in the overall population. No significant variation in OFS achievement was observed by chemotherapy status or triptorelin formulation (1-month vs. 3-month). This uniformity supports comparability of endocrine effect regardless of treatment combinations, such as chemotherapy status or type of endocrine therapy. Outliers in E2 levels were rare and will be described for each time point after the ongoing post-hoc analysis. Conclusion: In this second interim analysis of the ROSE study, triptorelin was shown to effectively and durably suppress ovarian function over time in premenopausal women with HR+ HER2− EBC, across multiple treatment settings. These findings support the role of long-term hormonal monitoring and reinforce the use of OFS as a key component of endocrine-based strategies in this population. Final analyses from the full cohort will help refine patient selection and personalization of OFS regimens. Citation Format: A. Fabi, G. V. Bianchi, F. Riccardi, A. Palazzo, L. Carbognin, A. Rossi, C. Mocerino, R. Ruocco, G. Mazzoli, G. Capri, E. Di Monte, V. Frescura, M. Fournier, G. Mauri, N. Bianco, M. Milano, E. Munzone. Sustained Ovarian Function Suppression with Triptorelin in Premenopausal HR+ HER2− Breast Cancer: Results from the Second Interim Analysis of the ROSE Study [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-07-08.