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

Aim. The aim of the present study was to evaluate the diagnostic sensitivity of [99mTc]methoxyisobutylisonitrile ([99mTc]MIBI) in a large series of patients with metastatic differentiated thyroid carcinoma (DTC), as compared with 131I-whole body scan (WBS) and other diagnostic imaging techniques. Methods. Eighty-four patients with known metastases from DTC where recruited during the course of replacement thyroxine therapy and undergone [99mTc]MIBI scan. All patients previously performed a 131I-WBS with thyroglobulin (Tg) measurement and neck ultrasound or computerized tomography, or magnetic resonance imaging, or bone scan or positron emission tomography (PET) scan. Results. Patients were divided in two groups: group A (n=50) with known metastases and positive at a previous 131I-WBS and group B (n=34) with known metastases, but negative at 131I-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 [99mTc]MIBI was greater in metastases without 131I uptake than in metastases with 131I uptake, although the difference was not statistically significant. Conclusion. 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 131I-WBS.