ERBB2 and breast carcinoma: To summarize descriptively health-related quality of life (HRQOL) and physical activity (PA) evaluated with a mobile application and wearable device among patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR + /HER2 −) advanced breast cancer (ABC) treated with first- or second-line palbociclib plus endocrine therapy (ET) or ET alone.