OVERVIEW OF MYELOMA BONE DISEASE

Multiple myeloma (MM) is the most common cancer to involve bone, with up to 90 percent of patients developing bone lesions [1]. The bone lesions are purely osteolytic in nature and do not heal in the vast majority of patients. Up to 60 percent of patients develop pathologic fractures over the course of their disease [2]. Bone disease is a hallmark of MM, and myeloma bone disease differs from bone metastasis caused by other tumors. Although myeloma and other osteolytic metastases induce increased osteoclastic bone destruction, in contrast with other tumors, once myeloma tumor burden exceeds 50 percent in a local area, osteoblast activity is either severely depressed or absent [3]. The basis for this severe imbalance between increased osteoclastic bone resorption and decreased bone formation is currently a topic of intensive investigation.

The clinical and economic impact of myeloma bone disease in patients with myeloma can be catastrophic. Saad and coworkers [4] retrospectively assessed the impact of pathologic fractures on survival of patients with malignant disease. Patients with myeloma had the highest incidence of fracture (43%) compared with patients with breast cancer, prostate cancer, and lung cancer, respectively. Myeloma patients who experienced pathologic fractures had at least a 20 percent increased risk of death compared with myeloma patients without pathologic fractures. Further, patients who had a prior skeletal-related event, which included pathologic fracture, spinal cord compression syndrome, surgery to bone, or radiation therapy to bone, were more likely to develop new pathologic fractures as compared with patients who did not have a prior skeletal-related event.