Tc 99m Sestamibi Scanning in Multiple Myeloma--a New look with SPECT-CT.

UNLABELLED: A variety of diagnostic tools including biochemistry, radiological imaging bone marrow studies and recently metabolic imaging with FDG PET are used for assessment of disease extent in myeloma.

AIM: To evaluate the role of metabolic imaging with Tc99m Sestamibi (Mibi) SPECT-CT in Multiple myeloma.

MATERIALS AND METHODS: Patients in various stages of Myeloma were scanned after 20mCi Tc99m Sestamibi was injected i/v. Whole body planar scans were obtained with a dual head gamma camera and SPECT-CT imaging was done. Images were analyzed for degree and extent of abnormal Mibi uptake, extent of lesions seen on low-dose CT and fusion of these images.

RESULTS: 112 Whole body Sestamibi Scans were performed in 84 patients (46 Males; 38 Females). Out of these 24 (28.5%) were recently diagnosed cases (Pre-therapy); 35 (41.7 %) were follow-up cases who had received Chemotherapy in the past (Post-therapy), there were 2 cases (2.3%) of Smouldering Myeloma, 4 cases (4.7%) of Plasmacytoma, 13 cases (15.5%) of MGUS (Monoclonal gammopathy of Unknown Significance) and 3 cases (3.6%) of suspected Myeloma (not biopsy confirmed). Myeloma lesions showed good concentration of Mibi. Additionally, the CT scan component of SP.ECT-CT allowed visualization of osteolytic lesions of myeloma. Mibi uptake becomes positive on scan earlier than radiological changes and in follow-up cases, the presence or absence of Mibi uptake could differentiate active from old burnt-out lesions. Whole body scan could detect additional lesions in Plasmacytoma patients. Patients of MGUS showed poor concentration of Sestamibi.

CONCLUSION: Whole body Sestamibi Imaging (WBSI) is very useful for evaluating the extent of disease in multiple myeloma. Being a metabolic imaging modality it is superior to radiological (X-ray or CT) assessment alone, and where FDG PET scan is not available, it is a valuable tool for myeloma assessment at a much lower cost.