Abstract PS3-09-02: Retrospective observational study of premenopausal ER+/HER2- patients in Greece with axillary tumor burden but low Oncotype DX® Recurrence Score who did not receive chemotherapy

Abstract Background The Oncotype DX® assay is a validated genomic test that aids in assessing the risk of distant recurrence and in predicting the potential benefit of adjuvant chemotherapy in patients with early-stage HR+, HER2- breast cancer. In premenopausal women with 1-3 positive lymph nodes (N1) and a Recurrence Score (RS) of 0-25, the RxPONDER trial demonstrated a 2.4% improvement in distant recurrence-free interval (DRFI) and a 4.9% improvement in invasive disease-free survival (IDFS) in pts receiving chemo-endocrine therapy compared to endocrine therapy alone. Pts who received only endocrine therapy had a DRFI of 93,9% and an IDFS of 89%. The aim of this observational study is to establish a registry and present data on DRFI and IDFS in premenopausal women with node-positive breast cancer and a low RS who, either by choice or due to comorbidities, did not receive chemotherapy and were treated with endocrine therapy alone (with/without ovarian function suppression - OFS). Methods We conducted a retrospective multicenter analysis across 9 institutions in Greece, focusing on pre- 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-09-02.