Abstract PS3-08-16: Real-world patterns of chemotherapy use in premenopausal women with node-negative early-stage HR+/HER2− breast cancer and intermediate genomic risk

Abstract Background: The optimal use of adjuvant chemotherapy in premenopausal women with early-stage hormone receptor-positive (HR+), HER2-negative (HER2−), node-negative breast cancer and intermediate Oncotype DX recurrence scores remains an area of clinical uncertainty. While prospective trials have provided clearer guidance for postmenopausal women, real-world treatment patterns and decision-making processes among premenopausal patients remain less well defined. Methods:We performed a retrospective analysis using the National Cancer Database (NCDB) to identify premenopausal women (<50 years) diagnosed from 2010-2021 with stage I-II, HR+/HER2−, node-negative breast cancer and recurrence scores of 11-25. We examined trends in chemotherapy omission, identified sociodemographic and clinical predictors of omission using multivariate logistic regression, and evaluated survival outcomes using Kaplan-Meier analysis and Cox regression. Results: Among 27,459 patients, 77.9% had stage I disease (n=21,408) and 22.1% had stage II (n=6,051). Chemotherapy was administered to 28.3% (n=7,773), while 71.7% (n=19,686) omitted it. Median age was 42 years among those who received chemotherapy and 44 years among those who did not. Among stage I patients, 24.2% received chemotherapy; in stage II, 42.6% received it. Chemotherapy use declined significantly from 35.4% in 2010 to 23.6% in 2021 (p < 0.001).Factors associated with chemotherapy omission included age 40-50 (OR 1.82, p < 0.001), diagnosis in 2014-2017 (OR 1.45, p < 0.001) or 2018-2021 (OR 1.58, p < 0.001) compared to 2010-2013, treatment at comprehensive (OR 1.09, p = 0.023), academic (OR 1.13, p = 0.002), or network centers (OR 1.11, p = 0.006) versus community centers, Medicare insurance (OR 1.81, p < 0.001), higher median income ≥$46,000 (OR 1.14, p = 0.002), and higher Charlson-Deyo scores (score 2: OR 1.23, p = 0.001; score ≥3: OR 1.32, p = 0.012).Conversely, chemotherapy omission was less likely among Black (OR 0.85, p < 0.001), South Asian (OR 0.68, p < 0.001), Hispanic (OR 0.83, p < 0.001), and rural patients (OR 0.88, p = 0.005) compared to non-Hispanic White and metropolitan patients, respectively.Five-year overall survival was similar between chemotherapy and no chemotherapy groups (98.1% vs. 97.6%, p = 0.244), with no significant survival benefit in Cox regression (HR 0.98, 95% CI 0.89-1.07, p = 0.51). Conclusions: Chemotherapy omission has increased over time among node negative premenopausal women with intermediate recurrence scores, yet practice variability remains. In this real-world population where treatment decisions were made by patients and physicians, there did not appear to be a survival benefit associated with chemotherapy.Ongoing prospective studies are further evaluating the safety of chemotherapy omission in premenopausal women with low genomic and higher anatomic risk, including the OFSET Trial (NRG-BR009, NCT05879926). Citation Format: I. Ajjawi, M. Wong, W. Wei, T. Park, J. Du, M. Rozenblit, S. Schellhorn, A. Kahn, N. Casasanta, E. Winer, M. Lustberg. Real-world patterns of chemotherapy use in premenopausal women with node-negative early-stage HR+/HER2− breast cancer and intermediate genomic risk [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 PS3-08-16.