265P - Effect of HER2-low-positive status on neoadjuvant chemotherapy and survival outcome of breast cancer: A 10-year dual-center retrospective study

Background

Various novel HER2-targeted antibody-conjugated drugs (ADCs) have shown satisfactory antitumor activity in HER2-low-positive breast cancer (BC). The effect of HER2 status on neoadjuvant chemotherapy (NAC) and survival outcome is controversial. It is urgent to clarify whether HER2-low-positive tumors have unique biological behavior and should be considered a new molecular subtype. In our study, a 10-year dual-center retrospective research was conducted to analyze the effect of HER2-low-positive status on NAC and survival outcome of BC.

Methods

We screened eligible BC patients and collected relevant information at the First Hospital of Jilin University and the the First Affiliated Hospital of Xi'an Jiaotong University from January 2010 to December 2020. The primary outcome indicator was pathologic complete response(pCR). The secondary outcome indicators were overall survival (OS) and disease-free survival (DFS).

Results

A total of 1027 patients were included in our study cohort, and 66.0% (678/1027) had HER2-low-positive tumors. Compared to HER2-zero, HER2-low-positive patients tended to have more lymph node metastasis, a larger proportion of hormone receptor (HR)-positive tumors, and a lower proliferation rate (Ki-67). The pCR rate of HER2-low-positive was lower than that of HER2-zero patients (19.3% vs 21.6%), especially in the HR-positive subgroup (12.00% vs 20.29%). However, multivariate logistic regression analysis showed that HER2 status was not an independent factor for predicting pCR. HER2-low-positive patients had a higher OS rate in the HR-positive subgroup. The Cox regression model analysis suggested that HER2-low-positive status did not affect the survival outcomes, regardless of DFS (p=0.308) or OS (p=0.066).

Conclusions

HER2-low-positive tumors have unique clinical and pathological characteristics, with a lower pCR rate in the HR-positive subgroup and better survival in the HR-negative subgroup compared to HER2-zero tumors. However, HER2-low-positive status is not an independent predictor of pCR or survival outcome. The authors have equally contributed to the study.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

This study was funded by the Innovation Capability Support Project of Shaanxi Province (No. 2023KJXX-032).

Disclosure

All authors have declared no conflicts of interest.