Objective  To explore the clinicopathological features of different expression states of HER-2 in patients with HER-2-negative breast cancer and their effect on neoadjuvant chemotherapy for breast cancer.

Methods  A total of 572 patients with HER-2 negative breast cancer admitted to Anyang Cancer Hospital from January 2019 to January 2022 were collected and based on HER-2 expression, divided into HER-2 0 (immunohistochemistlization 0) and HER-2 low expression groups (immunohistochemistlization1 + or 2 + (negative FISH results). The clinicopathological characteristics of the two groups were compared. Among them, 252 cases underwent neoadjuvant chemotherapy. The relationship between clinico-pathological feature and pathologic complete response were analyzed.

Results  The median age of the included patients was 49 (27~75), and the proportion of HER-2 0, HER-2 1 +, and HER-2 2 + patients were 48.5%, 31.29%, and 20.45%, respectively, and the proportion of HER-2 low expression was signif-icantly higher in HR + patients than in HR-negative patients (59.38% vs. 36.36%, P<0.001). The propor-tions of T3+4 (12.5% vs. 2.54%, P<0.001) and N3 (12.84% vs.3.62%, P<0.001) were significantly higher in the HER-2 low expression than in the HER-2 0 group, but the high expression of Ki-67 was lower (31.08% vs.52.90%, P<0.001). No matter in HR + (7.29% vs.15.38%, P=0.119) or HR-group (25.0% vs.40.0%, P=0.110), patients with HER-2 low expression had lower pCR rates than HER-2 0 patients, but it was not statistically significant.

Conclusion  HER-2 low expression has different clinicopatholog-ical features from HER-2 0, and neither HER-2 low expression nor HER-2 0 is an influencing factor in achieving pCR with neoadjuvant therapy.

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