Abstract PS3-10-12: Adjuvant chemotherapy and anthracycline use in older adults with high oncotype DX scores: A SEER-Medicare analysis

Abstract Background: Determining what adjuvant chemotherapy regimen to select in older patients with higher-risk, early-stage hormone receptor (HR)+, human epidermal growth factor receptor 2 (HER2)- breast cancers can be challenging. Patients with early-stage HR+/HER2-, node-negative breast cancer with high Oncotype DX recurrence scores (>31) may benefit from the addition of anthracyclines (1). However, it is not known whether this is true for older patients. The purpose of this study was to investigate outcomes based on Oncotype DX score and type of adjuvant treatment among older patients with early-stage, HR+/HER2- breast cancer using the Surveillance, Epidemiology, and End Results (SEER)-Medicare database. Methods: Using the SEER-Medicare database, we identified 5,439 women aged 66 years and older with a diagnosis of Stage I-III HR+/HER2- breast cancer between 2000 and 2019, and who had a recorded Oncotype DX score. We assessed patient characteristics, type of therapy received (anthracycline+taxane-based chemotherapy, taxane-based chemotherapy, or endocrine therapy), and Oncotype DX recurrence score (low [<11], intermediate [11-25], high [≥26]). Kaplan Meier survival curves were generated to assess overall survival (OS) and cancer-specific survival (CSS) based on Oncotype DX scores and therapy received. Results: Of the 5,439 patients in the cohort, most had an intermediate Oncotype DX score (60%), followed by a low Oncotype DX score (27%), and a high Oncotype DX score (13%). Most patients were aged 66-74 years (76%), followed by those aged 75-84 (22%). Only 1% were ≥85 years of age. Patients with a high Oncotype DX score had mostly node-negative disease (80%), with 17% having 1-3 positive nodes. Most patients in the high Oncotype DX score group received endocrine therapy alone (63%), followed by taxane-based chemotherapy (21%), and anthracycline+taxane-based chemotherapy (5%). Anthracyclines were used more often in patients aged 66-74 years. Most patients who received anthracyclines had a Charlson Comorbidity Index (CCI) of 0-1 (82%). In patients with a high Oncotype DX score and node-negative disease, anthracycline+taxane-based regimens did not improve OS or CSS when compared to taxane-based regimens and endocrine therapy. Importantly, the use of any chemotherapy did not improve OS and CSS in this group compared with endocrine therapy alone. In patients with a high Oncotype DX score and 1-3 positive nodes, anthracycline+taxane-based regimens did not improve OS and CSS when compared to taxane-based regimens and endocrine therapy. Likewise, the use of any chemotherapy did not improve OS and CSS in this group compared with endocrine therapy alone. Conclusion: The use of adjuvant chemotherapy, as well as the addition of anthracyclines, did not improve outcomes in patients aged ≥66 years with early-stage HR+/HER2- breast cancer and a high Oncotype DX score (RS≥26), regardless of nodal positivity. It is important to note that the overall number of patients who received an anthracycline+taxane-based regimen was small, so results should be interpreted with caution. This lack of benefit was seen even in a population with lower comorbidity scores, which suggests its use in highly selected individuals. The decision to treat patients with high-risk, early-stage HR+/HER2- breast cancer with adjuvant chemotherapy should be individualized, taking into account the limited benefits in OS compared with reports in younger individuals. 1. Chen, Nan. “San Antonio Breast Cancer Symposium .” GS3-03: Impact of Anthracyclines in High Genomic Risk Node-Negative HR+/HER2- Breast Cancer, 2024, https://sabcs.org/Portals/0/Documents/Embargoed/GS3-03%20Embargoed.pdf?ver=i2jS4VEzTIiDPEWdqDHRwA%3d%3d. Accessed 2025. Citation Format: A. R. Schreiber, E. Molina Kuna, E. Soto Pérez de Celis, J. R. Diamond. Adjuvant chemotherapy and anthracycline use in older adults with high oncotype DX scores: A SEER-Medicare analysis [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 PS3-10-12.