Clinicopathological characteristics of breast cancer patients with HER-2 low expression received neoadjuvant therapy

Introduction: 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.Methods: 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.Results: 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.Conclusions: 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.