Health-related quality of life of Canadian patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer.

397 Background: The EuroQol 5 Dimension 5 Level (EQ-5D-5L) is a validated tool that assesses health utility (HU) as a self-reported measure of health-related quality of life (HRQoL). This study aims to generate Canadian-specific HU data for patients with stable, HER2-positive (HER2+) metastatic breast cancer (mBC) receiving standard therapies. Methods: A cross-sectional study was conducted at McGill University Health Centre in Quebec, Canada. Eligibility criteria included: age ≥18 years, de novo or recurrent mBC, stable disease, and active treatment with a Health Canada-approved systemic therapy regimen (any line/time point on treatment). The EQ-5D-5L questionnaire was administered at every visit and each record was treated as a unique singular data point. The HU values were derived using the Canadian algorithm developed by Xie et al., 2016. The EQ-5D-5L measures HRQoL across five domains: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, and is scored on 5 levels ranging from one “no problems” to five “extreme problems”. A second part of the questionnaire includes a visual analogue scale (VAS) where respondents rank their overall health on scale of 0-100. The primary outcome was mean HU and standard deviation (SD) for HER2+ patients overall. Secondary outcomes included mean HU by hormone receptor (HR) status and describing patient responses to the questionnaire. Results: Between December 2022 and July 2023, a total of 81 HER2+ HU data points were included for analysis, representing 30 patients. For these patients, the mean age was 54.2 years (SD: 10.6). Most patients (58.3%) were on first line and had an Eastern Cooperative Oncology Group Performance Status of 0 (65.5%). The mean HU value was 0.83 (SD: 0.14, n=81). For patients with HR-positive mBC, the mean HU was 0.81 (SD: 0.14, n=44), while for patients with HR-negative mBC, it was 0.85 (SD: 0.13, n=37). The majority of patients reported “no problems” across all domains: mobility (69.1%), self-care (81.5%), usual activities (46.9%), pain/discomfort (35.8%), and anxiety/depression (58%). The mean VAS score was 77.3 (SD: 17.0). Conclusions: This study provides the first Canadian data on contemporary HU values for patients with HER2+ mBC, which reflects current HRQoL amidst a changing treatment landscape.