Change in HER2 Status After Neoadjuvant Chemotherapy and the Survival Impact

ABSTRACT Background The incidence of change in HER2 status in primary breast cancer after neoadjuvant chemotherapy (NAC) and whether the change affect prognosis is not well known. Patients and methods One hundred eighty-four patients who were treated with anthracycline- and/or taxane-based NAC and had non-pathologic complete response between 2003 and 2005 in our hospital were enrolled. Human epidermal growth factor receptor 2 (HER2) status was assessed in specimen by core needle biopsy before NAC and in residual tumor of surgical specimen. We determine the impact of change in HER2 status on recurrence-free survival (RFS). All patients had not received HER2-targeting agents during study period. HER2-positive was defined as 3+ by immunohistochemistry and/or amplification by fluorescent in situ hybridization. Association between clinicopathologic factors, including clinical T stage, estrogen receptor (ER), progesterone receptor (PR), Nuclear grade (NG), and clinical response, and change in HER2 status after NAC were determined. Result A median follow-up term was 74.1 months (range, 6.0 to 120.9 months). One hundred forty-nine of the 184 patients (80.9%) had HER2-negative tumors and 35 patients (19.0%) had HER2-positive tumor before NAC. HER2-negative tumors in 5 of the 149 patients (3.3%) changed to HER2-positive tumor. HER2-positive tumors in 7 of the 35 patients (20%) changed to HER2-negative tumor. In terms of RFS, there was no difference between patients with and without change in HER2 status in both of the 149 patients with HER2-negative tumors and 35 patients with HER2-positive tumors before NAC (p = 0.56, p = 0.96, respectively). Any clinicopathologic factors were not associated with change in HER2 status after NAC. Conclusion We herein reported the incidence of change in HER2 status after NAC with the large sample size. However, change in HER2 status did not seems to affect prognosis due to the small events in this study. Further well-powered study in needed to confirm the prognostic impact of change in HER2 status and needs of HER2-targeting agents for these populations. Disclosure All authors have declared no conflicts of interest.