17P - Clinical, pathological complete response and prognosis characteristics of HER2-low breast cancer in neoadjuvant chemotherapy setting: A retrospective analysis

Background

With the emergence of novel antibody-drug conjugates (ADC) drugs, HER2 low breast cancer may become a new clinical therapeutic subtype. The present study was conducted to evaluate the clinical, pathological complete response (pCR) and prognosis characteristics of HER2-low breast cancer in neoadjuvant chemotherapy setting.

Methods

Patients with HER2 negative breast cancer who have received neoadjuvant chemotherapy from January 2017 to December 2019 were retrospectively analyzed in a single center. HER2 negative breast cancer was divided into two groups: HER2-zero and HER2-low. HER2-zero was defined as IHC 0, and HER2-low was defined as IHC 1+ or IHC 2+/fluorescence in-situ hybridization (FISH) negative. The primary end point was pCR, secondary end points included disease free survival (DFS) and overall survival (OS).

Results

314 patients with HER2 negative breast cancer were enrolled. The proportion of HER2-low was 75.3% in HR-positive disease and 63.2% in triple-negative breast cancer (TNBC). In HR-positive breast cancer, HER2-low tumors presented less nodal involvement (p = 0.023) and earlier clinical stage (p = 0.015) compared to HER2-zero tumors. However, in TNBC, patients with HER2-low have a later clinical stage (p = 0.028). With the pCR defined as ypTis/0ypN0, there was no difference in pCR rates among general population, HR-positive disease and TNBC. However, with the pCR defined as ypT0ypN0, the pCR rate in HER2-low breast cancer was significantly lower than HER2-zero breast cancer in the general population (24.3% vs. 36.4%, P=0.032) and HR-positive subgroup (18.7% vs. 32.1%, P=0.035), but not for TNBC. Univariate and multivariate analysis demonstrated that HER2 status (low vs. zero) was an independent predictive factor for pCR (P = 0.013) in HR-positive breast cancer. There were no statistically significant differences in 3-year DFS and OS between HER2-low and HER2-zero breast cancer among general population, HR-positive disease and TNBC.

Conclusions

HER2-low breast cancer exhibit specific clinical features and different response to treatment associated with HR status in neoadjuvant chemotherapy setting.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Medical Science and Technique Foundation of Henan Province.

Disclosure

All authors have declared no conflicts of interest.