Abstract P1-03-03: Comparing staging assignments based on the 7th and 8th editions of the American Joint Committee on Cancer staging system for breast cancer
Authors: Brian R , Tseng J , Bao J , Jaskowiak N 
Published: May 2019

Background: The 8th edition of the American Joint Committee on Cancer (AJCC) staging system for breast cancer has redefined breast cancer staging to better represent the heterogeneity of the disease. The previously established TNM system reflected only tumor size (T), nodal status (N), and distant metastasis (M). The updated staging system introduces new clinical and pathological prognostic staging systems by incorporating tumor grade, tumor markers, and genomic assays. Prospective comparisons of staging assignment between AJCC 7th and 8th edition staging systems have not been performed in the United States. The objective of this study was to compare subjects' assigned stage between the AJCC 7th and 8th edition staging systems.

Methods: Data were collected from patients with non-metastatic breast carcinoma who presented to the University of Chicago between January 1, 2018 and May 31, 2018. Upstaging or downstaging was defined as an increase or decrease by one or more letter or number stages (i.e. from IIA to IIB or IB). Descriptive data were generated for all collected data. Analysis was performed in Stata 14.0.

Results: Clinical anatomic and prognostic stages were assigned to 246 patients while pathologic anatomic and prognostic stages were assigned to 142 patients. Forty-seven patients underwent neoadjuvant therapy and were not assigned a pathologic prognostic stage, while 57 patients had not undergone surgery at our institution by the end of the study period and were not assigned a pathologic stage. Two patients had lobular carcinomia in situ and were no longer considered to have a malignancy by the 8th edition staging system; anatomic staging was otherwise unchanged from 7th edition to 8th edition staging in this cohort. Of the 246 patients assigned clinical anatomic and prognostic stages, 48 patients were upstaged (19.5%), 37 were downstaged (15.0%), and 161 were not affected (65.5%) by prognostic staging. Of the 142 patients assigned pathologic anatomic and prognostic staging, nine patients were upstaged (6.3%), 32 were downstaged (22.5%), and 101 were not affected (71.1%) by prognostic staging. Four patients were eligible to be downstaged in pathologic prognostic staging by genomic assays such as Oncotype (consisting of Stage 1B or higher patients with T1N0M0 HER2 - ER + PR - Grade 3 disease or T2N0M0 HER2 - ER + disease). Of these patients, three had genomic assays performed by the end of the study period. Results from genomic assays did not affect the staging of these three patients.

Stage Changes with the AJCC 8th Edition Upstaged % (n)Downstaged % (n)No Change in Stage % (n)Clinical Stage19.5 (48)15.0 (37)65.5 (161)Pathologic Stage6.3 (9)22.5 (32)71.1 (101)

Conclusions: Approximately one third of breast cancer patients were assigned new clinical or pathologic stages with the AJCC 8th edition staging system. These findings confirm that implementation of the new criteria for staging will be important to many patients in discussions of treatment and prognosis.

Citation Format: Brian R, Tseng J, Bao J, Jaskowiak N. Comparing staging assignments based on the 7th and 8th editions of the American Joint Committee on Cancer staging system for breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-03-03.