ObjectiveTo summarize the correlation between human epidermal growth factor receptor 2 (HER2) gene expression and the efficacy of targeted therapy for patients with HER2-positive breast cancer, and to summarize the new progress in the study of HER2 gene copy number. MethodThe relevant literatures on researches of targeted therapy effectiveness for patients with HER2-positive breast cancer were retrieved and reviewed. ResultsHER2 gene copy number and HER2/centromere on chromosome 17 (CEP17) ratio were related to the prognosis of patients with HER2-positive breast cancer, and circulating tumor DNA sequencing was expected to be a predictive indicator of targeted therapy effectiveness. ConclusionHigher copy number of HER2 gene might be associated with a better prognosis of HER2-positive breast cancer, and HER2/CEP17 ratio and circulating tumour DNA are of some significances in evaluating treatment response of trastuzumab for patients with HER2-positive breast cancer.
