To investigate the effect of HER-2 expression on pathological complete response (pCR) and survival of breast cancer after neoadjuvant chemotherapy.

According to the inclusion and exclusion criteria, 171 patients who were diagnosed with breast cancer and received neoadjuvant chemotherapy in Qingdao Municipal Hospital from June 1, 2016 to December 31, 2020 were enrolled for a retrospective study. According to the immunohistochemical (IHC) results, the patients were divided into HER-2 (0) group, HER-2 low expression group [IHC: HER-2 (+ ) or HER-2 (2+ ) with ISH negative] and HER-2 positive group [IHC: HER-2 (3+ ) or HER-2 (2+ ) with ISH positive]. The clinicopathological features and prognostic parameters were compared among three groups using χ² test, Fisher exact test or Fisher-Freeman-Halton test. Kaplan-Meier method was used to draw the disease-free survival curve, and log-rank test was used to compare the survival rate between groups.

The patients were followed up for median 47 months (range: 2-54 months). There were 33 cases (19.3%, 33/171) in the HER-2 (0) group, 95 cases (55.6%, 95/171) in HER-2 low expression, and 43 cases (25.1%, 43/171) in HER-2 positive group. The hormone receptor (HR) status and MP grade showed no significant difference among three groups (χ²=8.497, P=0.014; H=9.406, P=0.009). After neoadjuvant chemotherapy, the pCR rates of HER-2 (0), HER-2 low expression and HER-2 positive group were 6.1% (2/33), 7.4% (7/95) and 20.9% (9/43), respectively, indicating no significant difference among three groups (χ²=5.744, P=0.052). According to the stratification of HR status, in HR positive patients, there was a statistically significant difference in pCR rate among three groups (χ²=7.618, P=0.011), and the pCR rate presented a significant difference between HER-2 low expression group and HER-2 positive group (P=0.033). In HR negative patients, there was no significant difference in pCR rate among three groups (χ²=1.498, P=0.513). The recurrence/metastasis rates of the three groups were 24.2% (8/33), 23.2% (22/95), 25.6% (11/43), respectively, with no significant difference (χ²=0.097, P=0.953). The disease-free survival of HER-2 (0), HER-2 low expression and HER-2 positive groups were 32 months (95%CI: 17-57 months), 44 months (95%CI: 40-49 months) and 58 months (95%CI: 56-60 months), respectively. There was no significant difference in disease-free survival among three groups (χ²=0.471, P=0.790).

Low expression of HER-2 cannot affect the pCR rate of breast cancer patients after neoadjuvant chemotherapy, and the patients with HER-2 low expression show no significantly different prognosis compared with HER-2 (0) patients.