Technetium-99m-sestamibi scintigraphy in multiple myeloma and related gammopathies: a useful tool for the identification and follow-up of myeloma bone disease.

BACKGROUND AND OBJECTIVES Technetium-99m 2-methoxy-isobutyl-isonitrile ((99m)Tc-sestamibi) has recently been proposed as a potential tracer in patients with multiple myeloma (MM), as its increased uptake in the bone marrow has been reported as indicator of myeloma activity. We evaluated the role of (99m)Tc-sestamibi scintigraphy in the detection of myeloma bone disease in MM and related gammopathies, and also assessed its relationship with clinical status and stage of the disease, focusing in particular on the early follow-up of a small series of MM patients treated with high-dose therapy. DESIGN AND METHODS Forty-six consecutive patients affected by MM or monoclonal gammopathy of undefined significance (MGUS) were studied by whole body scans obtained 20 minutes after administration of 740 MBq of (99m)Tc-sestamibi. A semiquantitative uptake score was used and scintigraphic findings were correlated with clinical and laboratory data. RESULTS All the MGUS patients showed a negative (99m)Tc-sestamibi scan. Among the 32 MM patients (25 with active disease and 7 in clinical remission) 24 showed a positive scan, while 8 presented only a physiologic uptake of the tracer. The uptake score correlated significantly with all the most relevant clinical variables. In the follow-up of 8 MM patients treated with high-dose chemotherapy (99m)Tc-sestamibi closely paralleled the activity of myeloma bone disease. Comparison with X-ray skeletal survey showed discordant results in 14 out of the overall 56 scans obtained (27%), with 10 cases of negative (99m)Tc-sestamibi scans but lytic bone lesions revealed by X-ray (7 of them were in clinical remission), and 4 negative X-ray surveys in patients with positive (99m)Tc-sestamibi scans. Overall sensitivity and specificity of (99m)Tc-sestamibi scintigraphy in detecting myeloma bone disease were 90% and 88%, respectively. INTERPRETATION AND CONCLUSIONS This study provides additional evidence indicating that (99m)Tc-sestamibi scintigraphy closely reflects myeloma disease activity in bone marrow, with very high sensitivity and specificity. (99m)Tc-sestamibi scintigraphy is therefore suggested as a reliable new tool for the staging and follow-up of myeloma bone disease.