Abstract P2-16-27: Risk factors of ipsilateral breast tumor recurrence in primary breast cancer patients who achieved pathological complete response after neoadjuvant chemotherapy
Authors: Matsuda Naoko , Hayashi Naoki , Tokui Ryu , Nakayama Takahiro , Yamauchi Hideko , Ishitobi Makoto 
Published: March 2020

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 &lt; 0.05 were considered statistically significant. Results: A median age of the 178 patients at diagnosis was 52 years (range, 30-72 years). At a median follow-up period of 5.4 years (range, 0.2-15.4 years), 5 patients (3%) had developed IBTR. Among the 178 patients, 82 patients had TNBC and 96 patients had HER2+ breast cancer. NAC with a combination of anthracycline and taxane regimens was sequentially delivered to 163 of the 178 patients (92%). In 96 HER2+ patients, trastuzumab containing regimen were done in 69 (72%) in NAC setting and 79 (82%) in adjuvant setting. Sentinel lymph node biopsy without axillary lymph node dissection was performed 98 (55%) of the patients. Seventy-nine (44%) had received axillary lymph node dissection. Subtype (ER+/HER2+, ER-/HER2+, or TNBC) after achieving pCR was not associated with 5-year IBTR (P= 0.6). In multivariate analysis, Clinical N-stage (N1 or more) was the only independent clinicopathological factor of associated 5-year IBTR in TNBC (P = 0.04). In HER2+ breast cancer, postoperative trastuzumab has a similar trend for 5-year IBTR (P = 0.07). Conclusions: We showed that clinical node-positive before NAC in TNBC and no receiving trastuzumab in HER2+ breast cancer were prognostic factor of 5-year IBTReven after achieving pCR.
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.