Stable or at least once HER2-low status during neoadjuvant chemotherapy confers survival benefit in patients with breast cancer

Abstract

Background Temporal heterogeneity in human epidermal growth factor receptor 2 (HER2) status may be associated with the prognosis of breast cancer. We aimed to clarify the relationship of HER2-low transition during neoadjuvant therapy with survival outcomes under the new classification of HER2 status. Methods This retrospective study was conducted based on the prospective database of breast cancer patients treated with neoadjuvant therapy from September 2013 to August 2020. Results This analysis enrolled 185 patients, including 44 patients with HER2-zero tumours, 93 patients with HER2-low tumours and 48 patients with HER2-positive tumours after neoadjuvant therapy. Nearly, 57.6% of HER2-zero tumours turned into HER2-low tumours after neoadjuvant therapy, while 25.0% of HER2-low patients changed to HER2-zero or HER2-positive tumours. We found that at least once diagnosis as HER2-low breast cancer was related to hormone receptor status (p < .001) and Ki-67 expression (p = .036). Patients ever diagnosed as HER2-low tumours had favourable clinicopathological features (less Ki-67 expression, lower pathological staging, etc.) as well as significantly better locoregional relapse-free survival (LRFS; p = .007) and overall survival (OS; p = .026) compared with those never exhibiting HER2-low expression. Furthermore, the 6-year OS rates were 94.2% (95% confidence interval (CI) 83.1–98.1), 88.7% (74.4–95.2) and 78.1% (65.4–86.6) for patients with stable, once and none HER2-low expression, respectively (adjusted HR, 0.514 [95%CI, 0.294–0.897], p = .019). Conclusions Our study first indicated in patients across all expression levels of HER2 that stable or at least once HER2-low status may confer favourable attributes including less malignant biological behaviour and long-term survival benefit for breast cancer receiving neoadjuvant therapy.