Real-World Data on Pathological Response and Survival Outcomes After Neoadjuvant Chemotherapy in HER2-Low Breast Cancer Patients

The data on pathological response and survival outcomes after neoadjuvant chemotherapy (NACT) in human epidermal growth factor receptor-2 (HER2)-low breast cancer (BC) is limited. We retrospectively retrieved clinicopathological data of 819 HER2-negative BC patients who received NACT between 2010 and 2020 from Shanghai Jiaotong University Breast Cancer Database. The results revealed that HER2-low expression was significantly associated with breast pathological complete response (pCR) in HER2-negative BC, but not with pCR or survival. Furthermore, estrogen receptor expression had a significantly prognostic impact on HER2-low BC. Background: Data on the pathological responses and survival outcomes after neoadjuvant chemotherapy (NACT) in human epidermal growth factor receptor-2 (HER2)-low breast cancer (BC) are lacking. This study aims to investigate this topic in the real world. Methods: Clinicopathological data from 819 HER2-negative BC patients who underwent NACT between 2010 and 2020 were retrospectively retrieved from the Shanghai Jiaotong University Breast Cancer Database. These patients were categorized into HER2-low and HER2-0 groups. Logistic analyses were conducted to identify predictors of complete pathological response (pCR) and breast pCR. Cox regression analyses were conducted to assess the factors associated with disease-free survival (DFS) and overall survival (OS). Kaplan-Meier (K-M) curves were generated to compare DFS and OS between HER2-low BC and HER2-0 BC. Results: Of the 819 BC patients, 669 (81.7%) had HER2-low tumors, and 150 (18.3%) had HER2-0 tumors. HER2-low BC had a significantly higher ratio of ER >= 10%, PR >= 20%, and Ki67 >= 15% than HER2-0 BC. A significantly higher breast pCR rate was observed in HER2-low BC than in HER2-0 BC (13.6% and 7.3%, respectively, P = .036). Age, HER2 status (low or 0), Ki67, and surgery options were associated with breast pCR in HER2-negative BC. In HER2-low BC, the pCR rate of ER >_ 10% BC was significantly lower than that of ER < 10% BC, but the DFS and OS of ER 10% BC were significantly higher. The K-M curve showed no significant differences in DFS or OS between HER2-low and HER2-0 BC. Cox regression revealed that ER expression and histological grade (III vs. I ' II) were significantly associated with survival in HER2-low BC. Conclusions: In this real-world data (RWD) study, a significantly higher breast pCR rate was found in HER2-low BC than in HER2-0 BC, although there was no significant difference in survival. Moreover, ER expression had a significant prognostic impact on HER2-low BC. Clinical Breast Cancer, Vol. 24, No. 5, 463-472