Breast cancer is the most common form of cancer in women. Modern breast cancer treatments have led to increased survival, but at the same time, increased risk for cardiotoxicity and development of heart failure. In this study, the investigators want to evaluate whether nicotinamide riboside can prevent cancer-related cardiac dysfunction in metastatic breast cancer patients scheduled for anthracycline therapy. Further, the investigators will evaluate change in signs of skeletal muscle injury and functional capacity.