Abstract P6-01-03: Change of HER2 status following neoadjuvant systemic therapy in primary breast cancer patients

Abstract

Abstract Background: The incidence of change in HER2 status in primary breast cancer after neoadjuvant chemotherapy (NAC) and whether the prognosis is affected by the change in HER2 status is not well known. Patients and Methods: Five hundred and eighty-eight patients who were treated with anthracycline- and/or taxane-based NAC and had non-pathologic complete response between 2001 and 2008 in our hospital were enrolled. Human epidermal growth factor receptor-2 (HER2) status was assessed in specimen by needle biopsy before NAC and on the residual tumor of surgical specimen. We determine the impact of change in HER2 status on recurrence-free survival (RFS). Twenty-eight patients had received trastuzumab with NAC, and 57 patients had received trastuzumab as adjuvant therapy. HER2-positive was defined as 3+ by immunohistochemistry and/or amplification by fluorescent in situ hybridization. Association between change in HER2 status after NAC and clinicopathologic factors, including age, clinical T stage, estrogen receptor (ER), progesterone receptor (PR), Nuclear grade (NG), lymphovascular invasion (LVI) and Trastuzumab usage (NAC and Adjuvant setting) were determined. Result: A median follow-up period was 57 months (range, 3 to 131 months). Four hundred eighty-nine of the 588 patients (83.1%) had HER2-negative tumors and 99 patients (16.8%) had HER2-positive tumor before NAC. In 11 of the 489 patients (2.2%) HER2-negative changed to HER2-positive.In 33 of the 99 patients (30%) HER2-positive changed to HER2-negative. In clinicopathologic factors, ER and PR positive before NAC were associated with incidence of change in HER2 status after NAC. Receiving trastuzumab was not correlated with incidence of change in HER2 status. In terms of RFS, there was no difference between patients with and without change in HER2 status in both of the 489 patients with HER2-negative tumors and 99 patients with HER2-positive tumors before NAC (p=0.26, p=0.23, respectively). Conclusion: We herein reported the incidence of change in HER2 status after NAC with the largest sample size. However, change in HER2 status did not seems to affect prognosis. Further prospective study is needed to confirm the prognostic impact of change in HER2 status. Citation Format: Atsushi Yoshida, Naoki Hayashi, Hiroshi Yagata, Koyu Suzuki, Seigo Nakamura, Hideko Yamauchi. Change of HER2 status following neoadjuvant systemic therapy in primary breast cancer patients [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 P6-01-03.