[The value of Tc-99m MIBI scintigraphy in active diseases and remission phase of Multiple Myeloma]

99mTc methoxy isobutyl isonitrile (99mTc MIBI) has been proposed as a tumor-seeking agent in malignant disease. The goal of this study is to evaluate the frequency distribution of the different patterns, intensity and extension of abnormal uptake identified in MIBI scan in relation with various clinical status of the patients diagnosed as multiple myeloma. Forty-three patients entered the study, including six patients with no prior treatment, 22 patients who receive autologous bone marrow graft and 15 patients with history of chemotherapy and radiotherapy. Plasma protein electrophoresis for monoclonal antibody, bone marrow biopsy and urine analysis for Bence-Jones protein has been carried out and standard criteria were used for diagnosis of active disease and remission phase for each patients. The extension of the lesions (E-score) on scintigraphy were categorized into E0-E3 by three nuclear physicians who were blinded to the patient’s clinical condition. I-score was also obtained with comparing the intensity of the lesions with intensity of myocardial uptake and classified as I0-I3. The sensitivity, specificity, positive predicative value and negative predictive value of 99mTc MIBI scan for determining active lesions and relapsed cases were 69%, 100%, 100% and 60%, respectively. Nineteen patients were initially thought to be in remission phase, but scintigraphy was abnormal in 5 cases who were diagnosed as active myeloma later in the course of the study. There was a significant correlation between clinical status and pattern, intensity and extension of the abnormal uptake of 99mTc-MIBI. Also a significant correlation between intensity and extension of the abnormal tracer uptake with serum monoclonal component and urine Bence-jones protein was noted, however no correlation between blood hemoglobulin and degree of extension in scintigraphy was seen. Our study suggests the patterns, extension and intensity of 99mTc MIBI uptake, in addition to the hematological findings are associated with disease activity and clinical status of the patients. Hence, in addition to the standard protocol, 99mTx-MIBI has a very high accuracy for detection of active myeloma disease and also can detect the group of patients who might benefit from treatment.