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
Authors: Ding Shuning , Wu Jiayi , Lin Caijin , Andriani Lisa , Chen Weilin , Liu Deyue , Zhu Li 
Published: March 2020

Abstract
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&lt;0.001 for C-index) with respect to DSS. In ILC cohort, the PS (C-index, 0.8281; AIC, 7124.423) was not superior to the AS (C-index, 0.8324; AIC, 7144.818; P=0.748 for C-index) in prognosis prediction with respect to DSS. Similar results were observed with respect to OS. Among three score systems specially designed for ILC patients, the score system defined by AS plus grade plus estrogen receptor and progesterone receptor (AS+GEP) allowed for better staging (C-index, 0.8085; AIC 7178.448). Detailed point assignments were listed in Table2.
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.
Table1. Distribution and survival outcomes by anatomic stages and prognostic stages in IDC cohort(N=166,084) and ILC cohort(N=18,475).StageIDC cohortILC cohortN (%)4-year DSS4-year OSN (%)4-year DSS5-year OSASIA85807(51.7)98.7195.687779(42.1)99.2395.99IB4500(2.7)97.7495.63326(1.8)98.6394.57IIA38186(23.0)95.2591.314596(24.9)97.4392.75IIB19762(11.9)91.2387.282628(14.2)96.3492.13IIIA10879(6.6)84.5381.462010(10.9)92.0587.14IIIB2831(1.7)75.3368.83202(1.1)74.6568.15IIIC4119(2.5)71.8267.22916(5.0)77.5573.94PSIA102448(61.7)98.8695.7012156(65.9)98.8095.27IB25722(15.5)95.7292.203553(19.3)95.4991.22IIA17329(10.4)91.0087.13757(4.1)95.1189.06IIB6599(4.0)86.7183.40541(2.9)91.6886.15IIIA7092(4.3)82.3078.281049(5.7)83.0177.15IIIB3431(2.1)76.0071.12313(1.7)72.3369.12IIIC3463(2.1)57.4352.3887(0.5)52.5348.09
Table 2. Univariate and multivariate analyses for factors associated with DSS and point assignment in ILC cohort.FactorUnivariate analysisMultivariate analysisModel AS+GModel AS+GEPHRPHRPHRPPointStageIA1/11/0IB1.84&lt;0.0011.750.3541.870.2690IIA3.34&lt;0.0013.15&lt;0.0013.15&lt;0.0011IIB5.31&lt;0.0014.91&lt;0.0015.04&lt;0.0012IIIA10.74&lt;0.0019.76&lt;0.0019.82&lt;0.0013IIIB30.16&lt;0.00126.49&lt;0.00123.86&lt;0.0014IIIC31.41&lt;0.00127.90&lt;0.00126.06&lt;0.0014Grade11/11/021.75&lt;0.0011.43&lt;0.0012.380.014134.30&lt;0.0012.47&lt;0.0012.06&lt;0.0011ER statusPositive1/1/0Negative6.85&lt;0.0012.51&lt;0.0011PR statusPositive1/1/0Negative2.47&lt;0.0011.75&lt;0.0011HER2 statusNegative1/Positive1.270.253Abbreviations for tables: AS, anatomic staging system; PS, prognostic staging system; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; DSS, disease -specific survival; OS, overall survival; HR, hazard ratio; ER, estrogen receptor; PR, progesterone receptor; HER2, human epidermal growth factor receptor 2; AS+G,anatomic stage plus grade; AS+GEP, anatomic stage plus grade plus estrogen receptor plus progesterone receptor.
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.