Technetium 99m sestamibi in multiple myeloma.

bone involvement. Destruction is mediated through normal osteoclasts, which respond to local osteoclast-activating microenvironment [7]. Technetium-99m 2methoxyisobutylisonitrile (TC-99m MIBI) is a lipophilic agent that accumulates within living malignant cells due to the higher transmembrane electrical potential as a consequence of the higher metabolic rate than in the surrounding normal cells [2]. It has been reported to be useful in detecting disease lesions in multiple myeloma [1,10,17,19,27]. In comparative studies, Tc-99m MIBI scintigraphy proved to be superior to skeletal X-ray survey in detecting bone and bone marrow involvement [8,9]. In myeloma, the isotope bone scan may be falsely negative because of purely osteolytic lesions, but may not be completely normal if there is some osteoblastic activity, particularly in relation to pathological fracture. Other radiopharmaceuticals which have shown promise in the investigation of myeloma include gallium-67, Tc-99m tetrofosmin and thallium-201 [10,29]. Tc-99m-MIBI has been reported to be distributed as a diffuse and/or focal uptake in bone marrow of patients with active myeloma disease. Furthermore, a semiquantitative score based on the extension and intensity of the diffuse uptake on whole–body scan showed a direct correlation with plasma cell infiltration, clinical status and stage of the disease [19]. In patients undergoing chemotherapy, the findings of baseline Tc-99m MIBI scintigraphy are strongly correlated with the clinical outcome at follow-up. These results suggested a potential role of Tc-99m-MIBI in the follow-up of patients with multiple myeloma [22].