This prospective, single-arm pilot study evaluates the feasibility and acceptability of a novel Patient Support Coordinator (PSC) model for women with advanced or high-risk breast cancer in an outpatient oncology setting. The PSC model is designed to address gaps in serious illness communication by embedding a trained, non-clinical coordinator into routine care pathways to provide longitudinal psychosocial support and facilitate values-based discussions. The primary hypothesis posits that the PSC intervention will be perceived as acceptable by participants, defined by a population median score of ≥12 out of 16 on both the Client Satisfaction Questionnaire (CSQ-4) and the Feeling Heard and Understood (FHU) scale. Additionally, the study assesses feasibility through metrics such as enrollment and retention rates, as well as the successful integration of PSC-documented patient priorities into clinical workflows. By using a convergent parallel mixed-methods design, the study aims to generate a complete view of how this lay-led model complements existing supportive care infrastructure at the National Cancer Centre Singapore.