Methods: Separate surveys will be used to assess utilities and productivity in HER2+ metastatic breast cancer (MBC). To capture utilities health state descriptions or vignettes describing progressive disease, stable disease, and seven grade 3/4 adverse events (diarrhoea, fatigue, anaemia, leukopenia, anorexia, decreases in left ventricular ejection fraction (LVEF), and skin rash) will be developed. The vignettes will be developed based on a literature review and in depth interviews with women with MBC in the Netherlands and Sweden. Clinical experts in both countries will review the health states for content validity. The health states will be translated using forward and back translation. Members of the general public will rate the states (100 men and women in NL; 100 women aged 50+ in Sweden) using the visual analogue scale and Time Trade Off method to determine utility values. In a separate survey women who are currently being treated or have recently completed their treatment for MBC will be surveyed regarding the impact of disease on their ability to work using a validated work productivity measure (Work Productivity and Activity Impairment) in women in the Netherlands and Sweden.