Disappointing results with Tc-99m Tetrofosmin for detecting medullary thyroid carcinoma metastases comparison with Tc-99m VDMSA and Tl-201

Purpose: This prospective study assessed the detectability of metastatic lesions by Tc-99m tetrofosmin in medullary thyroid carcinoma and to compare the results with Tc-99m penta dimercapto succinic acid (VDMSA) and TI-201. Methods: A prospective study was performed on 24 patients (10 men, 14 women; ages 23 to 76 years) with medullary thyroid carcinoma after total thyroidectomy. Five cases were sporadic and 19 were familial. After the injection of 740 MBq (20 mCi) tetrofosmin, 740 MBq (20 mCi) VDMSA and 74 MBq (20 mCi) TI-201, whole-body scans and 5-minute static images of the head, neck, chest, abdomen and pelvis were obtained. All scintigraphic studies were compared with calcitonin levels, radiologic findings, histopathologic results, and clinical follow-up. Results: Thirty-four metastatic sites were detected in 12 patients on the basis clinical, radiologic, and histopathologic findings. Patients were divided into three groups according to the calcitonin levels and scintigraphic findings. Group 1 consisted of patients with elevated calcitonin levels and positive scintigraphic findings. Among 34 metastatic sites, 30 could be detected with VDMSA. Only 21 and 20 metastatic sites could be visualized with TI-201 and tetrofosmin, respectively. All 30 lesions showed intense VDMSA uptake but only faint or no uptake with TI-201 and tetrofosmin. Patients in group 2 were accepted to have micrometastases. In this group, calcitonin was minimally elevated, and the results of all three scintigraphs were negative. Group 3 included patients with true-negative results. All patients had normal calcitonin levels and negative results of scintigraphic studies. Conclusions: Tetrofosmin has no role in the detection of medullary thyroid carcinoma metastases. These results show that VDMSA is clearly superior to TI-201 and tetrofosmin in the follow-up of patients with medullary thyroid carcinoma.