Abstract P3-11-15: Different clinical usefulness of AJCC response criteria according to the subtypes in stage II/III breast cancer patients after neoadjuvant chemotherapy

Background: Response to neoadjuvant chemotherapy (NAC) is a useful prognostic marker for relapse and overall survival but their prognostic role is distinct in different breast cancer subtypes. Pathologic complete response (pCR) is a current gold standard for evaluating response to NAC. Despite its clinical usefulness, discrimination into pCR and non-pCR is too simple because non-pCR includes broad range of actual responses from very good partial response to even progressive disease. American Joint Committee on Cancer (AJCC) 7th edition proposed response criteria for NAC based on precise clinical stage before NAC and pathologic staging after NAC. The purpose of this study is to evaluate the clinical usefulness of AJCC response criteria in each breast cancer subtypes. Patients and Methods: Patients with clinical stage II or III breast cancer treated with NAC at Seoul National University Hospital were enrolled and reviewed retrospectively. AJCC response criteria for NAC were adopted from the AJCC 7th edition: complete response (CR), absence of invasive carcinoma in both breast and lymph node; partial response (PR), decrease in either or both T or N stage; no response (NR), no change or increase in either or both T or N stage. The definition of each breast cancer subtypes were adopted from 2011 St Gallen Consensus Panel for current study. Results: From January 2009 to December 2010, 183 patients were enrolled in the study with median follow up period of 38.0 months. AJCC response was significantly associated with relapse free survival (RFS) (P Conclusion : AJCC criteria is an easily reproducible tool for response evaluation for breast cancer patients in NAC setting compared with classically used pCR in all breast cancer subgroups except luminal A. Citation Format: Yaewon Yang, Seock-Ah Im, Tae-Yong Kim, Kyung-Hun Lee, Bhumsuk Keam, Sae-Won Han, Do-Youn Oh, Tae-You Kim, Wonshik Han, Hyeong-Gon Moon, In Ae Park, Dong-Young Noh. Different clinical usefulness of AJCC response criteria according to the subtypes in stage II/III breast cancer patients after neoadjuvant chemotherapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-11-15.