Expert consensus on the clinical diagnosis and targeted therapy of HER2 breast cancer (2023 edition).

Human epidermal growth factor receptor 2 (HER2) is an important driver gene and prognostic indicator of breast cancer and also a key predictor of HER2-targeted therapies. The emerging anti-HER2 drugs have greatly changed the diagnosis and treatment modalities of breast cancer and dramatically improved the prognosis of HER2-positive breast cancer patients. To optimize the treatment of HER2 breast cancer an update of expert consensus on HER2 positive breast cancer was made to adjust the different recommendation levels from early stage to metastatic stage. Meanwhile, antibody-drug conjugate (ADC) like trastuzumab deruxtecan (T-Dxd) has been shown to have great efficacy in HER2-positive and HER2 low expression breast cancer patients. Clinically, on the basis of the original definition for HER2-negative breast cancer, patients with HER2 immunohistochemistry (IHC) 1+ or IHC 2+ and in-situ hybridization (ISH)-negative are defined as low HER2 expression (HER2-low). As both the low expression and the positive expression of the HER2 protein is clinically significant for disease treatment and prognosis, we added a new chapter of HER2 low to recommend a proper regimen for this kind of patients. In this consensus, we also talk about the importance of clinical research, real world evidence, biosimilars and so on. In addition, the whole-course management of HER2 breast cancer is even more critical during pandemic of coronavirus disease 2019 (COVID-19). An approach that gives preference to "low-toxicity regimens and oral preparations" are also recommended.
Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tbcr.amegroups.com/article/view/10.21037/tbcr-22-48/coif). XW serves as an unpaid editorial member of Translational Breast Cancer Research from December 2020 to November 2022. SSW, CG, FJ, YY, QZ, ES and JW serve as the unpaid editorial members of Translational Breast Cancer Research from March 2022 to April 2024. SW and YL serve as the unpaid editorial members of Translational Breast Cancer Research from May 2021 to April 2023. JL serves as an unpaid Managing Editor of Translational Breast Cancer Research from November 2019 to October 2024. ZJ serves as the Editor-in-Chief of Translational Breast Cancer Research. The other authors have no conflicts of interest to declare.
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