Comparison of In-111 octreotide and Tc-99m (V) DMSA scintigraphy in the detection of medullary thyroid tumor foci in patients with elevated levels oftumor markers after surgery

Purpose: In this retrospective study, the authors evaluated the utility of In-111 octreotide (OctreoScan) and Tc-99m (V) DMSA scintigraphy for the loc alization of recurrent metastatic tumor foci in patients with medullary thy roid cancer (MTC) and compared the findings with those of conventional radi ologic imaging methods. Methods: The scintigraphic images were compared with computed tomography (C T) and magnetic resonance imaging (MRI) and ultrasonography (US) in 14 pati ents (8 men, 6 women; age range, 22 to 74 years) with elevated calcitonin a nd carcinoembryonic antigen levels after total thyroidectomy. All scintigra phic image findings were evaluated qualitatively as mild uptake (+) and mod erate to marked uptake (++). Results: In-111 octreotide may be superior to Tc-99m (V) DMSA for the detec tion of tumor foci of patients with MTC on a patient basis (78.5% versus 57 .1%) and on a lesion basis (44.1% versus 30.2%). The sensitivity rate for I n-111 octreotide (78.5%) was also similar to that of CT and MRI on a patien t basis. Conversely, the combined use of Tc-99m (V) DMSA and In-111 octreot ide revealed the best sensitivity rate (85.7%) on a patient basis, whereas the combined use of CT and MRI showed the best sensitivity rate (81.3%) on a lesion basis. Conclusions: These findings suggest that In-111 octreotide is superior to T c-99m (V) DMSA and has a similar sensitivity rate to CT and MRI for the dia gnosis of recurrent or metastatic MTC. Although the combined use of In-111 octreotide and Tc-99m (V) DMSA was most sensitive, the combined use of CT a nd MRI with radionuclide imaging methods may better detect more metastatic tumor foci.