**1. Introduction**

Breast cancer is the most common cancer in women with a worldwide annual incidence of 2.3 million cases and 685,000 death per year [1]. There is a clear correlation between bone health and breast cancer [2], as bone mineral density can be severely reduced through early menopause or endocrine therapy, including aromatase inhibitors [3]. Secondly, there is also a clear relationship between osteo-oncologic treatment including densoumab and bisphosphonates and outcome in early breast cancer [4]. Thirdly, in stage IV breast cancer, bone is the most common site of metastasis [5].

Disease-specific events related to bone metastasis include complications, such as spinal cord and nerve compression and pathological fractures, needing surgical interventions and/or radiotherapy. This is therefore a major endpoint in treatment of metastatic breast cancer, since targeted therapy has the potential to significantly improve outcome in early and metastatic breast cancer [6].

This chapter will give you an overview on bone health management and prevention in early and metastatic breast cancer patients.
