2025 Update of the Taiwan Expert Consensus on Hormone Receptor-Positive Metastatic Breast Cancer Management

Hormone receptor-positive metastatic breast cancer remains a major clinical burden and is characterized by sequential endocrine resistance over the disease course. In 2023, the Taiwan Breast Cancer Society (TBCS) published an expert consensus to support real-world decision-making in Taiwan. Subsequently, rapid advances in biomarker-informed strategies (e.g., estrogen receptor 1 and PI3K/AKT pathway alterations), endocrine partners, estrogen receptor (ER)-targeting agents (including oral selective ER degraders and emerging protein degraders), and the expanding role of antibody-drug conjugates based on human epidermal growth factor receptor 2 expression categories have materially increased the complexity of treatment selection and sequencing. Therefore, TBCS convened an expert panel to update the previous consensus while preserving its foundational framework and eight-chapter structure: risk evaluation and biomarker testing (I/II), first-line treatment selection (I/II), second-line treatment selection (I/II), and treatment options other than endocrine-based approaches (I/II). A multidisciplinary panel conducted a systematic literature review and iterative discussions using a modified Delphi process to identify the key clinical questions, update and refine statements where new evidence was practice-changing, and maintain continuity with the 2023 Consensus. The panel formulated updated recommendations, assigned levels of evidence and strengths of recommendations, and the key updates were integrated into practical treatment algorithms reflecting Taiwan's practice considerations. This updated consensus provides a continuity-based, yet evidence-responsive framework to facilitate the integration of emerging therapies into clinical practice in Taiwan and the Asia-Pacific region.