Abstract P2-16-27: Risk factors of ipsilateral breast tumor recurrence in primary breast cancer patients who achieved pathological complete response after neoadjuvant chemotherapy

Abstract

Background: Pathologic complete response (pCR) is an early surrogate marker of long-term survival in human epidermal growth factor receptor 2-positive (HER2+) and triple negative breast cancer (TNBC). However, it is difficult to predict patients who should avoid breast-conserving therapy (BCT) even after achieving pCR by neoadjuvant chemotherapy (NAC) with respect to ipsilateral breast tumor recurrence (IBTR). We aimed to assess the risk of IBTR in pCR patients who underwent BCT after NAC. Patients and methods: We retrospectively reviewed clinicopathological characteristics of 178 TNBC or HER2+ primary breast cancer patients with pCR who underwent BCT after NAC in 2 institutes between 2002 and 2017. Histological type and grade were defined according to the World Health Organization classification system. Estrogen receptor (ER), progesterone receptor (PR), and HER2 status were determined from the surgical specimens. ER and PR were assessed by immunohistochemical staining. HER2 was considered positive if reported as 3+ on immunohistochemical staining or if those tumors reported as 2+ were amplified on fluorescence in situ hybridization (FISH). pCR was defined as no involvement of invasive ductal carcinoma in breast and lymph nodes. All patients who had node-positive before NAC had axillary lymph node dissection even if assessed as clinically node-negative after NAC (ycN0). The 5-year IBTR-free survival was estimated in each subtype. The risk factors of IBTR, including the age at diagnosis, clinical T-stage, clinical N-stage, histological grade, neoadjuvant regimen, pathological N-status, and postoperative chemotherapy, were estimated using the log-rank test for univariate analysis. P-values Citation Format: Naoko Matsuda, Naoki Hayashi, Ryu Tokui, Takahiro Nakayama, Hideko Yamauchi, Makoto Ishitobi. Risk factors of ipsilateral breast tumor recurrence in primary breast cancer patients who achieved pathological complete response after neoadjuvant chemotherapy [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 P2-16-27.