Abstract PS3-09-10: Higher Breast Tumor Grades Could More Likely Benefit from Extended Adjuvant Endocrine Therapy

Abstract Background: The Breast Cancer Index (BCI) (Biotheranostics, Inc. A Hologic Company.) is a gene-expression based biomarker utilized in both node negative and node positive, early-stage HR-positive breast cancer patients who may benefit from extended adjuvant endocrine therapy (AET) based on the tests’ comprehensive predictive and prognostic evidence. However, the association between BCI and clinicopathological factors remains unclear. We aimed to identify associations between predictive BCI scores of HR-positive breast cancer patients with various clinicopathological factors. Methods: We conducted a single center retrospective study using the BCI to evaluate differences in clinicopathologic factors among HR-positive breast cancer patients. Variables of interest included age, tumor grade, race, node status, number of nodes involved, HER-2 status, and ER/PR staining intensity. BCI scores to predict recurrence were classified as “Yes” (likely to benefit from extended AET) or “No.” Fisher’s exact test was used to compare categorical variables between patients with positive and negative BCI test result. The Wilcoxon rank sum test was applied to compare ordinal variables. A p-value of <0.05 was statistically significant. All statistical analyses were performed with R software. Results: 52 patients with HR-positive breast cancer had BCI testing from 2014-2025 at our institution. Most patients were >55 years old, identified as White, both ER and PR positive (compared with ER or PR positive only), and HER2 negative, and had moderately high to high intensity ER/PR staining. Most patients were node negative (71%). 25.5% of patients had grade 3 tumor. Of this study cohort, 25 (48%) had a predictive BCI score. Patients with higher tumor grades had more predictive BCI scores (p=0.0293). Age, intensity of ER/PR staining, and number of nodes involved had no significant effect on the BCI score (Table 1,1Wilcoxon Rank Sum test, 2Fisher’s Exact test). Conclusion: Higher tumor grades were more likely to have a predictive BCI score compared with lower tumor grades, indicating higher recurrence risk and/or more benefit from extended AET. Nodal status was not a statistically significant factor. Larger, multicenter studies with varied patient populations are needed to further validate these findings. Citation Format: Y. Ogunsesan, M. Lin, R. Dutta, R. Brazauskas, A. Szabo, L. N. Chaudhary, Y. C. Cheng, S. Kamaraju. Higher Breast Tumor Grades Could More Likely Benefit from Extended Adjuvant Endocrine Therapy [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 PS3-09-10.