Abstract PO1-18-02: Histologic grade is a better predictor of specific survival than Ki67 in localized ER+/HER2- breast cancer: a real-world study

Abstract Introduction: Breast cancer (BC) is the most common cancer in women. The determination of prognostic factors is relevant for the decision of systemic therapy. Objective: To determine, in the real world, the prognostic role of Ki67 and histologic grade (HG) in patients with non-metastatic BC in two cancer centers; an academic and a community hospital. Methodology: Retrospective analysis of a longitudinal BC patients registry. Clinicopathological characteristics and disease specific survival (DSS) of women diagnosed in stages I/II/III between the years 2012-2021 were analyzed. Results: We evaluated 3,969 cases that met the inclusion criteria. In the univariate analysis, prognostic factors significantly associated with DSS were: reason for consultation (screening vs symptoms), stage, hormone receptor status, HG and Ki67. On multivariate analysis, stage III, Ki67 ≥20%, and GH3 were significantly associated with a risk of death of 4.41, 2.52, and 1.92; respectively, regardless of the treatment center and BC subtype. However, in the hormone receptor positive (HR+)/HER2 + group the HG presented greater discriminatory power than Ki67. Hazard ratio 2.0 for both, but not statistically significant for Ki67. The ROC-AUC curves for Ki67 indicated that the best cut-off point for DSS was 20%, for the entire cohort and also for the HR+/HER2- group. Conclusions: The behavior of the prognostic variables was expected and coincided with the literature. HG seems to be a better predictor of specific mortality in HR+ BC. Ki67 showed a cut-off value consistent with that suggested by expert consensus. Citation Format: Cesar SÁNCHEZ, Cataldo Alejandro, Benjamin Walbaum, FRANCISCO ACEVEDO, Christine Constabel, Antoine Saure, Pablo Rey. Histologic grade is a better predictor of specific survival than Ki67 in localized ER+/HER2- breast cancer: a real-world study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-18-02.