Circulating biomarkers for diagnosis and therapeutic monitoring in bone metastasis

Bone is a frequent site of metastasis for multiple types of solid tumors in organs such as prostate, breast, lung, etc., accounting for significant morbidities and mortalities of afflicted patients. One of the major problems of bone metastasis is lack of biomarkers for early diagnosis and for monitoring therapeutic responses. Medical imaging modalities such as computerized tomography, magnetic resonance imaging, and radioactive isotope-based bone scans are currently standard clinical practices, yet these imaging techniques are limited to detect early lesions or to accurately monitor the metastatic disease progression during standard and/or experimental therapies. Accordingly, development of novel blood biomarkers rationalizes extensive basic research and clinical development. This review article covers the up-to-date information on protein- and cell-based biomarkers of bone metastasis that are currently used in the clinical practices and also are under development.