HER2-low status may predict poor neoadjuvant chemotherapy response in HR-negative breast cancer: a real-world multicenter study

Objective We aimed to investigate the impact of human epidermal growth factor receptor 2 status (human epidermal growth factor receptor 2-low versus human epidermal growth factor receptor 2-zero) on pathological response to neoadjuvant chemotherapy and survival outcomes in early-stage breast cancer. Methods Patients with primary invasive breast cancer received neoadjuvant chemotherapy between July 2018 and July 2021 were identified from six hospitals. The primary efficacy end-point was total pathological complete response. The second short-term efficacy end-points include breast pathological complete response, axillary lymph nodes pathological complete response and the score of Miller-Payne grade. Long-term efficacy end-point was disease-free survival. Results 429 patients with human epidermal growth factor receptor 2 negative invasive tumors were included, 267 (62.24%) had human epidermal growth factor receptor 2-low tumors. Hormone receptor-positive patients had a higher percentage of human epidermal growth factor receptor 2-low tumors compared to hormone receptor-negative patients (71.97% versus 42.14%). The pathological response rate was significantly lower in human epidermal growth factor receptor 2-low tumors than in human epidermal growth factor receptor 2-zero tumors for total patients in univariate analysis, including the rates of total pathological complete response (5.2% versus 14.2%), breast pathological complete response (6.4% versus 17.3%), nodes pathological complete response (26.3% versus 37.7%) and MP4-5 (21.2% versus 33.8%). Subgroup analysis showed that the rates of total pathological complete response, breast pathological complete response and MP4-5 were also significantly lower in human epidermal growth factor receptor 2-low tumors versus human epidermal growth factor receptor 2-zero tumors in both univariate and multivariate analysis in hormone receptor-negative subgroup. With the median follow-up of 24 months, disease-free survival was comparable between these two subgroups (P = 0.816). Conclusions Our results demonstrate that human epidermal growth factor receptor 2-low tumors achieved a significantly lower pathological complete response rate with conventional chemotherapy than those with human epidermal growth factor receptor 2-zero tumors, especially for hormone receptor-negative group. Large, randomized, prospective studies are needed to confirm our data and further evaluate the prognostic value of human epidermal growth factor receptor 2-low expression. Our results demonstrate that patients with human epidermal growth factor receptor 2-low breast tumors achieved a significantly lower pathological complete response rate with conventional chemotherapy than those with human epidermal growth factor receptor 2-zero tumors, especially for hormone receptor-negative group.