99mTc-MIBI Scintigraphy Versus 131I Whole Body Scan in the Follow-up of Patients with Differentiated Thyroid Carcinoma

Thyroid cancer is the most common endocrine malignancy. More than 90% of primary thyroid cancers are papillary or follicular types, together termed Differentiated Thyroid Cancers (DTC). The aim of this study was to assess to what extent 99mTc-MIBI Whole Body Scan (WBS) improves detectability of negative 131I scan in follow-up of patients with DTC. This descriptive and prospective study was performed over 40 patients with DTC who were referred to Dr. Dabiri Nuclear Medicine Center from 2004-2005. Six months after total thyroidectomy and 131I ablation therapy, all patients underwent 131I 99mTc-MIBI WBS. Serum thyroglobulin was measured by radioimmunoassay method. Serum TSH levels was >30 μU mL-1 in all patients. 99mTc-MIBI showed 93.75% sensitivity and 87.5% specificity. The figures for 131I scan were 87.5 and 100%, respectively. It is concluded that considering the slightly higher sensitivity of 99mTc-MIBI, this radio tracer can be used for follow-up of patients with negative 131I study and patients on suppression therapy.