Abstract P5-06-23: Comparison of the AJCC eighth edition prognostic stage and anatomic stage in different histological breast cancer types and proposal of a novel score system

Background: The objective of the current study was to validate the prognostic staging system (PS) proposed in AJCC 8th edition staging manual among patients with invasive ductal carcinoma (IDC) and patients with invasive lobular carcinoma (ILC) respectively, and to compare the predictive performances of PS in both cohorts. Method: Patients diagnosed with IDC and ILC from 2010 to 2015 in the Surveillance, Epidemiology and End Results (SEER) database were retrospectively identified. Patients were restaged according to anatomic staging system (AS) and PS. Disease-specific survival (DSS) and overall survival (OS) were estimated by Kaplan-Meier method. The predictive performances of different staging systems were quantified and compared based on Harrell’s concordance index (C-index) and Akaike information criterion (AIC) calculated from Cox models. New staging score systems were established by assigning points to DSS-associated prognostic factors to improve risk stratification. Results: A total of 184,541 female patients were included in the final analyses, with 166,084 (90%) cases in the IDC cohort while 18,475 (10%) cases in the ILC cohort. Stage distribution and survival outcomes of different stages were showed in Table1. In IDC cohort, the PS (C-index, 0.8281; AIC, 110274.5) showed superiority in risk stratification compared with the AS (C-index, 0.8125; AIC, 112537.0; P Conclusion: Compared with AS, the PS provided more accurate stratification for patients with IDC, but not for patients with ILC. The AS+GEP score system may fit ILC tumors better. Further investigation was needed to refine tumor staging. Citation Format: Shuning Ding, Jiayi Wu, Caijin Lin, Lisa Andriani, Weilin Chen, Deyue Liu, Li Zhu. Comparison of the AJCC eighth edition prognostic stage and anatomic stage in different histological breast cancer types and proposal of a novel score system [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-23.