Chinese expert consensus on clinical diagnosis and treatment of breast cancer targeting HER2

Background: 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. Both the low expression and the positive expression of the HER2 protein are clinically significant for disease treatment and prognosis. Methods: (I) Establishment of expert group: the expert group consists of experts from departments such as medical oncology, breast surgery, and pathology; (II) literature search: mainly conducted in English databases (such as PubMed, Embase, and Cochrane Library) with a search cutoff date of June 1, 2025; (III) assessment of evidence quality and recommendation strength: evidence quality and recommendation opinions are graded based on the evidence category and recommendation level of the Chinese Society of Clinical Oncology (CSCO) guidelines. Results: The emerging anti-HER2 drugs have greatly changed the diagnosis and treatment modalities of breast cancer and dramatically improved the prognosis of patients with HER2 expression in breast cancer. To optimize the treatment, an update of expert consensus on breast cancer with HER2 expression was made to adjust the different recommendation levels from early stage to metastatic stage. In this consensus, we also talk about the importance of clinical research, real-world evidence, biosimilars and so on. Conclusions: The overarching goal of this consensus is to deliver individualized treatment strategies that not only prolong survival but also enhance quality of life, ensuring HER2-positive breast cancer patients receive the most advanced, patient-centered care available.