Sensitivity of [99mTc]methoxyisobutylisonitrile scan in patients with metastatic differentiated thyroid cancer

The aim of the present study was to evaluate the diagnostic sensitivity of [(99m)Tc]methoxyisobutylisonitrile ([(99m)Tc]MIBI) in a large series of patients with metastatic differentiated thyroid carcinoma (DTC), as compared with (131)I-whole body scan (WBS) and other diagnostic imaging techniques.

Eighty-four patients with known metastases from DTC where recruited during the course of replacement thyroxine therapy and undergone [(99m)Tc]MIBI scan. All patients previously performed a (131)I-WBS with thyroglobulin (Tg) measurement and neck ultrasound or computerized tomography, or magnetic resonance imaging, or bone scan or positron emission tomography (PET) scan.

Patients were divided in two groups: group A (n=50) with known metastases and positive at a previous (131)I-WBS and group B (n=34) with known metastases, but negative at (131)I-WBS. All patients had elevated serum Tg level in absence of replacement therapy. Technetium-99m-MIBI scan showed 76.2% sensitivity in detecting metastases, Tg during opotherapy 64.3%, and the other imaging techniques combined 86.9%. Sensitivity of [(99m)Tc]MIBI was greater in metastases without (131)I uptake than in metastases with (131)I uptake, although the difference was not statistically significant.

Technetium-99m-MIBI scan improves sensitivity of Tg measurement in patients with suspected metastases from DTC during the course of opotherapy and is a useful alternative to fluorodeoxyglucose-PET or other imaging techniques in patients with elevated serum Tg and negative (131)I-WBS.