A multi-centre, randomised study, to determine the feasibility of recruiting men and women with metastatic HER2 positive breast cancer to a study with a baseline MRI scan followed by randomising to surveillance by two further six-monthly MRI scans versus no further surveillance of the brain. Qualitative research (focus groups and/or interviews) and monitoring of approach and consent with SEAR framework will be embedded within the trial to achieve the primary endpoint and explore challenges with study implementation and delivery.