Implications of bone metastases and the benefits of bone-targeted therapy

Several cancers, including those originating in the breast, prostate, and lung, exhibit a propensity to metastasize to bone, resulting in debilitating skeletal complications. These sequelae, such as intractable pain, pathologic fractures, spinal compression, and hypercalcemia, greatly erode the patients' quality of life. Bisphosphonates, a class of antiresorptive drugs, are now the mainstay of the treatment of skeletal-related events in myeloma bone disease and many solid cancers with bone metastases. Current evidence indicates that newer-generation nitrogen-containing bisphosphonates, particularly zoledronic acid, are potent inhibitors of bone resorption. In addition, increased understanding of the pathogenesis of bone metastasis has resulted in the development of several bone-targeted therapies including a monoclonal antibody targeting the receptor activator of nuclear factor (NF)-κB ligand (RANKL). In this review, clinical evidence regarding the efficacy and safety of currently available bone-targeted therapies including bisphosphonates and anti-RANKL monoclonal antibody in the treatment of bone metastasis due to breast cancer, prostate cancer, lung cancer, and multiple myeloma bone disease will be summarized.