Differences In Pathologic Complete Response Rates Between HER2 3+ And HER2 2+/FISH Positive Breast Cancer Patients After Neoadjuvant Therapy And Analysis Of The Causes

Objective: To investigate whether there is a difference in pathologic complete response(pCR)rates after neoadjuvant therapy between human epidermal growth factor receptor 2(HER2)3+ and HER2 2+ in HER2-positive breast cancer patients,and to explore the reasons for the difference.Methods: Clinical and pathological information of 295 HER2-positive breast cancer patients admitted to the Breast Center of the Fourth Hospital of Hebei Medical University from January 2018 to November 2020 who had completed neoadjuvant chemotherapy and anti-HER2 targeted therapy and received surgical treatment were summarized and analyzed.The patients were divided into HER2 3+ and HER2 2+/FISH+ groups according to the expression of HER2 protein.The pCR rates of the two groups after neoadjuvant treatment were compared,and the subgroup analysis was carried out according to clinical and pathological factors.Logistic regression analysis was used for univariate and multivariate analysis to explore the factors affecting the pCR rate of HER2-positive breast cancer patients after neoadjuvant therapy.Results: A total of 295 HER2-positive breast cancer patients were enrolled,including 33 HER2 2+/FISH+ patients and 262 HER2 3+ patients.The proportion of patients with high expression of hormone receptor(HR)in the HER2 2+/FISH+ group was higher than that in the HER2 3+ group.The pCR rate after neoadjuvant therapy was significantly different between the HER2 2+/FISH+ group and the HER2 3+ group(P < 0.05).There was no significant difference in the pCR rate between HER2 2+/FISH+ and HER2 3+patients in the subgroup ≤ 35 years old,the subgroup with low HR expression,the subgroup with clinical TNM stage II,and the subgroup with 4cycles of anti-HER2 targeted therapy during neoadjuvant therapy(P > 0.05).There were significant differences in the pCR rates between the HER22+/FISH+ group and the HER2 3+ patients in the age > 55 subgroup,the 35 <age ≤55 subgroup,the HR high expression subgroup,the clinical TNM stage III subgroup and the HER2 targeted therapy subgroup for ≥6 cycles during neoadjuvant therapy(P < 0.05).Logistic regression analysis showed that clinical TNM stage,HER2 expression,hormone receptor(HR)expression,Ki-67 index and neoadjuvant anti-HER2 targeted therapy are the factors that affect the pCR rate of HER2-positive breast cancer patients after neoadjuvant therapy(P < 0.05).Conclusions:1.After the neoadjuvant treatment of anti-HER2 targeted therapy combined with chemotherapy,the pCR rate of HER2 3+ breast cancer patients is higher than that of HER2 2+/FISH+ patients.2.Logistic regression analysis showed that cTNM II stage,HER2 3+,low expression of HR,high Ki-67 index and dual HER2-blockade therapy are the factors that increase the pCR rate of HER2 positive breast cancer patients after neoadjuvant anti-HER2 treatment.3.HR expression and the efficacy of anti-HER2-targeted therapy are responsible for the difference in pCR rates between HER2 3 + and HER2 2+/FISH+ breast cancer patients after neoadjuvant therapy.