Abstract
The acronym CRAB summarizes the most typical clinical manifestations of multiple myeloma, these being hypercalcemia, renal failure, anemia, and bone disease. CRAB can be used to distinguish between active, symptomatic multiple myeloma and monoclonal gammopathy of undermined significance or smoldering myeloma. The distinction is relevant not only for classification and diagnosis but also for therapy. CRAB factors influence the prognosis of multiple myeloma. However, it is unclear whether the presence of CRAB factors has an influence on the prognosis of myeloma treated with novel agents. In the current study, patients with hypercalcemia and bone disease showed a significantly worse prognosis, whereas anemia and renal failure showed no difference in survival. Novel agents used for treatment of patients with renal failure suggested a favorable outcome compared with conventional therapy. Bone disease was the most common factor and may have the strongest prognostic value in symptomatic myeloma patients using novel agents.