近年来，人类表皮生长因子受体-2（HER2）低表达的乳腺恶性肿瘤已成为研究的热点，但HER-2低表达是否代表了乳腺癌的一种特殊亚型仍不清楚。然而，这种分子类型在新辅助治疗阶段需要更有效的治疗方案。本研究纳入自2011年10月至2019年5月在哈尔滨医科大学肿瘤医院接受新辅助治疗的乳腺癌患者，为单中心回顾性研究。共纳入1053例接受术前治疗的乳腺癌患者，其中包括279例（26%）HER-2低表达患者。HER-2低表达组中50岁以下的患者比例高于其他两种分子亚型组（p=0.047，62.0% vs. 57.2%和52.5%），Ki67指数超过15%的患者的比例低于HER-2阴性和HER-2阳性患者（p<0.001，50.2% vs. 63.6%和71.5%）。大多数HER-2低表达患者为激素受体（HR）阳性（p<0.001，85.7% vs. 60.4%和36.0%），其在新辅助治疗后的病理完全缓解（pCR）率显著低于HER-2阴性和HER-2阳性患者（p<0.001，5.7% vs. 11.8%和20.5%）。亚组分析结果显示，HER-2低表达的HR阳性患者与HER-2阳性患者相比，具有较低的pCR率（p<0.001，4.6% vs. 14.6%）和客观反应率（ORR）（p=0.001，77.8% vs. 91.0%），而与HER-2阴性患者相比，在这些率上没有显著差异。HER-2低、HER-2阴性和HER-2阳性患者在至多67个月（中位随访时间）的总生存率（OS）和无病生存率（DFS）方面没有显著差异。Cox比例风险模型的结果显示Ki67指数和T分期（T3）是DFS的独立影响因素。在OS方面，Ki67指数，P53，T分期和客观反应（OR）是HER-2低表达患者OS的独立影响因素。总的来说，需要进一步的研究来确认HER-2低表达是一种特殊的乳腺癌分子亚型。HER-2低表达患者在新辅助治疗中的疗效相对较差，而新辅助治疗的疗效可以预测HER-2低表达患者的预后。由S. Karger AG, Basel出版。

Human epidermal growth factor receptor-2 (HER2) low expression breast malignant tumors have become a research hotspot in recent years, but it is still unclear whether HER-2 low expression represents a special subtype of breast cancer. However, this molecular type requires more effective treatment regimens in the neoadjuvant therapy stage.This study enrolled breast cancer patients who were treated at Harbin Medical University Cancer Hospital for neoadjuvant treatment between October 2011 and May 2019 and was a single-center retrospective study.A total of 1053 breast cancer patients who received preoperative therapy, including 279 (26%) HER-2 low expression patients, were included in this retrospective study. The HER-2 low expression group had a higher proportion of patients under 50 years old than the other two molecular subtype groups (p=0.047, 62.0% vs. 57.2% and 52.5%), and the percentage of patients with Ki67 index above 15% was lower than that in HER-2 negative and HER-2 positive patients (p<0.001, 50.2% vs. 63.6% and 71.5%). Most of the patients with HER-2 low expression were hormone receptor (HR) positive (p<0.001, 85.7% vs. 60.4% and 36.0%), and their pathologic complete response (pCR) rate after neoadjuvant therapy was significantly lower than that of HER-2 negative and HER-2 positive patients (p<0.001, 5.7% vs. 11.8% and 20.5%). The results of the subgroup analysis showed HR-positive patients with HER-2 low expression had a lower pCR rate (p<0.001, 4.6% vs. 14.6%) and objective response rate (ORR) (p=0.001, 77.8% vs. 91.0%) than HER-2 positive patients and had no significant difference in these rates compared to HER-2 negative patients. There were no significant differences in overall survival (OS) and disease-free survival (DFS) up to 67 months (the median follow-up time) among HER-2 low, HER-2 negative and HER-2 positive patients. The results of cox hazard proportional showed that the Ki67 index and T stage (T3) were independent influencing factors for DFS. In terms of OS, Ki67 index, P53, T stage and objective response (OR) were independent influencing factors for OS in HER-2 low expression patients.In general, further studies are needed to confirm that HER-2 low expression is a special breast cancer molecular subtype. The efficacy of neoadjuvant therapy in patients with HER-2 low expression is relatively poor, and the efficacy of neoadjuvant therapy can predict the prognosis of patients with HER-2 low expression.The Author(s). Published by S. Karger AG, Basel.