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

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.

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

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.

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.

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.