Advances in neoadjuvant therapy for HER2-positive breast cancers: a narrative review.

Background and Objective: Breast cancer (BC) is currently the most frequently diagnosed cancer and the primary cause of cancer-related death among women worldwide. Human epidermal growth factor receptor type 2 (HER2)-positive BC accounts for 14.5-15% of all BCs, with a relatively poor prognosis. Neoadjuvant therapy (NAT) has become a preferred treatment option for HER2+ BCs. With the continuous emergence of various clinical trials and new treatment concepts in BC, the NAT model has changed from chemotherapy alone to the neoadjuvant combination of anti-HER2-targeted therapy with chemotherapy, neoadjuvant endocrine therapy, and so on. Therefore, an up-to-date review is needed to inform the selection of NAT strategies for HER2+ BCs. Methods: This review was administrated with literature from the PubMed database. Manuscripts were searched using the following keywords: "neoadjuvant" or "preoperative", "breast cancer" or "breast neoplasm", "HER2+" or "HER2-positive", titles and abstracts were screened and evaluated independently by two authors. Information relating to the efficacy and safety profile of NAT for patients with HER2+ BCs were included and analyzed qualitatively. Only English-language articles were included. Key Content and Findings: This review discusses the neoadjuvant situation for the surgical management of HER2-positive BCs around the world. In this paper, we describe the efficacy assessment of NAT, analyze clinical effect and toxicity of chemotherapy, and targeted therapy, including monoclonal antibody, tyrosine kinase inhibitors (TKIs) and antibody-drug conjugates (ADCs), and other neoadjuvant treatments in HER2+ BC. The data shows while overall survival is the standard endpoint for efficacy, pathological complete response have been implemented more and more frequently in clinical trials for its convenience. Dual-targeted therapy plus chemotherapy exhibited favorable efficacy in most cases, meanwhile other treatment strategies such as combinations without chemotherapy or including CDK4/6 agents may be applicable in specific situation. Conclusions: As an important part of BC treatment, NAT is lingering in the stage of continuous development, especially for patients with HER2-positive BC. The challenges we are facing today in this field are dose de-escalation without reducing efficacy and choose suitable combination of agents in clinical practice. Moreover, new biomarkers are warrant for individualize treatment.