Clinical usefulness of 99mTc-MIBI scintigraphy in the postsurgical evaluation of patients with differentiated thyroid cancer.

OBJECTIVE Tc-methoxyisobutyl isonitrile (MIBI) has been reported to show considerable clinical utility in the study of many neoplastic diseases. The aim of our study was to investigate the possible role of Tc-MIBI in the initial follow-up of patients with differentiated thyroid cancer (DTC) for detecting residual thyroid uptake and/or loco-regional/distant metastases. METHODS Eighty-two patients with DTC (61 women, 21 men; mean age: 49 years) were studied after total or near-total thyroidectomy (not earlier than 3 months after thyroidectomy but before they underwent radioiodine therapy). About 20 min after the intravenous administration of 370 MBq of Tc-MIBI, planar images (and, if necessary, tomographic images, single photon emission tomography) of the cervical and thoracic regions were recorded and compared with posttherapy radioiodine scanning and thyreoglobulin serum levels. RESULTS MIBI scans detected thyroid remnants in 53 of 82 patients (65%) and metastatic foci in 10 of 11 (91%) patients, in whom a standard activity of 1110 MBq of I administered following MIBI scan had shown the presence of thyroid remnants or metastatic foci, respectively. One metastatic patient was false negative for both MIBI scan and post-I dose whole body scan. CONCLUSION Our data indicate that an MIBI scan has a high sensitivity in detecting metastatic lesions from DTC. Therefore, an MIBI scan after thyroidectomy and immediately before radioiodine treatment may be clinically useful for choosing the best therapeutic approach in terms of either ablative or therapeutic I activity for both thyroid remnants and/or DTC metastases and for evaluating surgical reappraisal of metastatic lymph nodes.