The major clinical manifestation of multiple myeloma is related to osteolytic bone destruction. Bone disease can lead to pathologic fractures, spinal cord compression, hypercalcemia, and pain, and is a major cause of morbidity and mortality. These complications result from asynchronous bone turnover wherein increased osteoclastic bone resorption is not accompanied by a comparable increase in bone formation. The increase in osteoclast activity in myeloma is mediated by the release of osteoclast-stimulating factors. These factors are produced locally in the bone marrow microenvironment by cells of tumor and non-tumor origin. Bisphosphonates are specific inhibitors of osteoclastic activity and are effective in the treatment of hypercalcemia associated with malignancies and may reduce the development of skeletal complications. Recent studies have revealed that new molecules such as the receptor activator of nuclear factor-kappa B (RANK), its ligand (RANKL), osteoprotegerin (OPG), and macrophage inflammatory protein-1a are implicated in osteoclast activation and differentiation, while proteins such as dikkopf-1 inhibit osteoblastic bone formation. These new molecules seem to interfere not only with the biology of myeloma bone destruction but also with tumour growth and survival, creating novel targets for the development of new antimyeloma treatment. Recent studies with monoclonal antibodies to RANKL appear promising. The management of the bone disease in multiple myeloma include the bisphosphonates, radiotherapy and surgery.
Multiple myeloma; bone disease; osteoclast activity; biphosphonates