294P - Prognostic significance and evolution of HER2 zero, HER2 low and HER2 positive in breast cancer after neoadjuvant treatment

Background

With the development of anti-HER2 targeted antibody-drug conjugates, HER2 low has attracted a lot of attention in breast cancer (BC). It's significant to study the pathological response of HER2 zero, HER2 low and HER2 positive BC after neoadjuvant treatment and the HER2 status evolution.

Methods

A retrospective study was conducted at National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College. Data from patients who were diagnosed with BC between 2015 and 2021 at our center and who had received neoadjuvant treatment were collected. The pathological complete response (pCR) rate of HER2 zero, HER2 low, and HER2 positive was analyzed. And the analysis of HER2 status evolution were carried out.

Results

1173 patients with BC who had received neoadjuvant treatment were collected. 11.85% of the patients (n=193) achieved pCR, and 88.15% of the patients (n=1034) were non-pCR. Among 526 patients with available baseline biopsy reports and matched pathological reports after neoadjuvant treatment, HER2 low BC was related to the lowest rate of pCR, followed by HER2 zero and HER2 positive BC (13.79% vs. 20.00% vs. 40.20%, respectively, p=0.000). Of the 526 patients, 381 were hormone-receptor-positive BC, and 145 were triple-negative breast cancer (TNBC) on baseline biopsy. In 381 patients with hormone-receptor-positive BC, HER2 low BC was also related to the lowest rate of pCR, followed by HER2 zero and HER2 positive BC as well (9.14% vs. 12.28% vs. 36.22%, respectively, p=0.000). A similar trend was also observed in TNBC without a statistically significant difference. On the converting of HER2 zero, HER2 low and HER2 positive before and after neoadjuvant treatment, HER2 zero has the highest discordance rate and 58.21% of HER2 zero on baseline biopsy converted into the other two types after neoadjuvant treatment. The conversion rates of HER2 low and HER2 positive on baseline biopsy were 28.10% and 14.43%, respectively.

Conclusions

Compared with HER2 zero and HER2 positive, HER2 low has the lowest pCR rate after neoadjuvant treatment. Besides, HER2 zero had the highest incidence of conversion to other HER2 statuses after neoadjuvant treatment.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.