Determination of medullary thyroid carcinoma metastases by Tl-201, Tc-99(m)(V)DMSA, Tc-99(m)-MIBI and Tc-99(m)-tetrofosmin

Medullary carcinoma of the thyroid (MCT) is malignancy derived from the par afollicular cells (or C-cells) of the thyroid. It is usually sporadic, alth ough it is familial in some cases. Several scintigraphic procedures can pro vide information regarding the primary and metastatic foci of the tumour. W e performed whole-body scanning to establish the pathology of MCT using Tl- 201, Tc-99(m)(V)DMSA and Tc-99(m)-MIBI in 14 patients, and found average se nsitivities of 73%, 82% and 81%, respectively. Moreover, we also scanned th ree patients with Tc-99(m)-tetrofosmin and identified two of four pathologi cal foci as well as residual thyroid tissue. The sensitivities of Tl-201, T c-99(m)(V)DMSA and Tc-99(m)-MIBI were 100%, 100% and 85% in identifying lym phadenopathies; 40%, 50% and 71% for soft tissue foci; 100%, 100% and 100% for foci in pulmonary parenchyma; and 100%, 66% and 100% for recurrences in thyroid gland. Although Tc-99(m)(V)DMSA identified all bony metastases in three patients (100%), Tc-99(m)-MIBI detected only two of three foci (66%) and Tl-201 none. Tl-201, Tc-99(m)-MIB and Tc-99(m)-tetrofosmin accumulated in residual thyroid tissue, but Tc-99(m)(V)DMSA did not, as expected. We co nclude that these agents were complementary, since they had different sensi tivities in different tissues. The tumour-seeking properties of tetrofosmin are to be evaluated in a larger series. ((C) 1999 Lippincott Williams & Wi lkins).