Abstract PS3-09-25: Factors Associated With Real-World Use of Ovarian Function Suppression Versus Tamoxifen Alone in Premenopausal Women With Early-Stage HR+/HER2- Breast Cancer

Abstract Background Approximately 16% of new breast cancer diagnoses occur in premenopausal women. Young women with estrogen receptor-positive (ER+) human epidermal growth factor receptor 2-negative (HER2–) breast cancer may be considered for adjuvant endocrine therapy (ET) with tamoxifen (Tam) alone or with ovarian function suppression (OFS) plus Tam or aromatase inhibitor (AI). Optimal adjuvant therapy for this population is of significant interest because young age at diagnosis is associated with a worse prognosis. The SOFT and TEXT trials have demonstrated a benefit of OFS compared to Tam alone in premenopausal women with high risk. Use of OFS, however, may be associated with increased toxicity and may be under-utilized in clinical practice. This study evaluated the real-world use of OFS in premenopausal women aged 3.0 cm, lymph node-positive disease, higher grade tumors, and to have received chemotherapy. A multivariable logistic regression analysis revealed that age at diagnosis and grade were factors significantly associated with the choice of Tam alone versus OFS for adjuvant therapy. ET was discontinued early due to toxicity in 14.5% and 20 patients discontinued ET due to recurrence (16 in the Tam alone group and 4 in the OFS group). At a median follow-up of 66 months, a total of 64 breast cancer recurrences had occurred, 13 in the OFS group and 51 in the Tam alone arm. Recurrence was not statistically different between the OFS and Tam groups when controlling for age, BMI, grade, and stage (HR 0.12 [95% CI: 0.60–2.09], p=0.7237). Conclusion Data from the SOFT and TEXT trials support consideration of maximal hormone suppression with OFS in premenopausal women. Our study highlights the likely underutilization of OFS, even in this high-risk population in the community setting, likely due to increased concern for toxicity. However, these concerns are not supported by the increased rate of early discontinuation in the OFS group. Although not statistically significant, a higher number of recurrences were noted in the tamoxifen alone group. Additional research is warranted to optimize the selection of patients who might benefit most from maximal hormonal blockade with OFS compared to Tam alone. Citation Format: P. Saha, C. Sanchez, O. Israel, L. Eldridge, K. Kuchta, K. A. Yao. Factors Associated With Real-World Use of Ovarian Function Suppression Versus Tamoxifen Alone in Premenopausal Women With Early-Stage HR+/HER2- Breast Cancer [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 PS3-09-25.