Abstract P1-07-32: Validation of the new AJCC eighth edition of the TNM classification for breast cancer with a single center breast cancer cohort
Authors: Kim J-Y , Lim JE , Jung HH , Cho SY , Cho EY , Lee SK , Yu JH , Lee JE , Kim SW , Nam SJ , Park YH , Ahn JS , Im Y-H 
Published: February 2018

Abstract
Introduction : Our understanding of biology of breast cancer has led to significant changes in diagnostic and therapeutic approaches for breast cancer, The new eighth edition of the TNM classification of the AJCC for breast cancer (BC) determined by a multidisciplinary team of BC experts incorporate biologic factors, such as tumor grade, estrogen and progesterone receptor (ER and PR) expression, human epidermal growth factor 2 (HER2) expression, and gene expression prognostic panels in addition to traditional anatomic factors. In this study, we aimed to evaluate prognostic value of this new staging system compared to previous AJCC 7th staging system using single center, long term followed BC cohort.
Methods : We conducted a retrospective analysis of women with stage I, II, or III BC who underwent curative surgery with/without adjuvant systemic therapy at Samsung Medical Center between July 2004 and December 2008 (n=3,029). We excluded patients who received neoadjuvant therapy (n=183), and patients with missing information about immunohistochemistry (n=7), HER2 status (n=82) or histologic grade (n=74). The final sample size was 2,683.
Results: Of 2,683 BCs, 1,689 (63%) were hormone receptor (HR)-positive(+), 244(9%) were HR+ andHER2+, 289(11%) were HR-negative(-) andHER2+, 461(17%) were triple negative BCs. According to AJCC 7th pathologic staging system, there were 1,135 of stage IA, 4 of IB, 803 of stage IIA, 368 of stage IIB, 258 of stage IIIA, 11 of stage IIIB and 104 of stage IIIC. In terms of 10 year overall survival (OS) according to AJCC 7th staging system, 95.8% in stage IA, 100% in stage IB, 93.5% in IIA, 86.0% in stage IIB, 85.6% in stage IIIA, 90.9% in stage IIIB and 63.6% in stage IIIC were observed (p&lt;0.001) (Medial follow up duration : 118 months). According to AJCC 8th clinical staging system, there were 722 of stage IA, 693 of IB, 306 of stage IIA, 201 of stage IIB, 251 of stage IIIA, 137 of stage IIIB and 160 of stage IIIC. In terms of 10 year overall survival (OS) according to new staging system, 96.7% in stage IA, 96.6% in stage IB, 91.4% in IIA, 92.1% in stage IIB, 86.2% in stage IIIA, 80.2% in stage IIIB and 66.8% in stage IIIC were observed (p&lt;0.001). However, 213 BCs(7.9%) could not be staged by AJCC 8th clinical staging system. In depth analysis will be presented.
Conclusions: AJCC 8th clinical staging system provides a good prognostic value and makes up for the weakness of AJCC 7th anatomical pathologic staging. But this system cannot count whole pathologic stages. Modification of AJCC 8th clinical staging system would be warranted.
Citation Format: Kim J-Y, Lim JE, Jung HH, Cho SY, Cho EY, Lee SK, Yu JH, Lee JE, Kim SW, Nam SJ, Park YH, Ahn JS, Im Y-H. Validation of the new AJCC eighth edition of the TNM classification for breast cancer with a single center breast cancer cohort [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-07-32.