Abstract 193P
Background
The HER2-low classification (immunohistochemistry [IHC] 1+ or IHC2+ and in situ hybridization–negative) is a new breast cancer (BC) category, established with the introduction of novel anti-HER2 antibody-drug conjugates. We investigated the characteristics, clinical outcomes, and relapse patterns of patients with HER2-low and HER2-zero (IHC 0) BC in an Asian population.
Methods
We retrospectively identified patients with stage I-III BC who were treated with neoadjuvant chemotherapy and underwent curative surgery between 2014 and 2018 at Asan Medical Center, Seoul, Korea. Eligible patients were those with HER2-low or HER2-zero BC.
Results
A total of 818 and 754 patients with HER2-zero and HER2-low BC were consecutively included in this analysis, respectively. The HER2-low group had significantly more hormone receptor [HR]–positive patients (80% vs 54%, p < 0.001). The HER2-zero group had a significantly higher proportion of patients who achieved pathologic complete responses (16% vs 10%, p < 0.001), whereas there was no significant difference in this regard between the HR-positive and HR-negative subgroups (p = 0.4 for the HR-positive group, p = 0.3 for the HR-negative group). With a median follow-up duration of 5.6 years (95% CI 5.4-5.7), patients with HER2-low BC had higher 5-year overall survival (OS) and disease-free survival (DFS) rates (5-year OS: 92.4% [95% CI 90.3-94.4] vs 84.1% [81.5-86.7], p < 0.001; 5-Year DFS 78.6% [75.5-81.9] vs 73.1% [69.3-76.0], p = 0.003). In the multivariate analysis including age, T stage, N stage, histologic grade, Ki-67 expression, HR status, and HER2 status, HER2-zero BC was significantly associated with worse OS (hazard ratio [HR] 1.9 [95% CI 1.3-2.6], p = 0.001) but not DFS (HR 1.2 [0.9-1.5], p = 0.07). Patients with HER2-low BC had a peak relapse rate at 30 postoperative months, whereas the peak relapse rate occurred at 12 postoperative months in the HER2-zero BC group.
Conclusions
In this study, HER2-low and HER2-zero BC were associated with distinct biological features and clinical outcomes after neoadjuvant chemotherapy, suggesting that different management approaches will be needed for HER2-low BC.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
K.H. Jung: Financial Interests, Personal, Advisory Role: Astra-Zeneca, BIXINK, MSD, Novartis, Pfizer, Roche, Takeda, Everest Medicine. S. Kim: Financial Interests, Personal, Invited Speaker: Novartis; Financial Interests, Personal, Advisory Board: AstraZeneca, Lilly, DaeHwa Pharma, ISU Abx, Daiich-Sankyo, Beigene; Financial Interests, Personal, Ownership Interest: Genopeaks, Neogene TC; Financial Interests, Institutional, Research Grant: Novartis, Sanofi-Genzyme, DongKook Pharm Co. All other authors have declared no conflicts of interest.