99mTc-Depreotide Scintigraphy Versus18F-FDG-PET In The Diagnosis Of Radioiodine-Negative Thyroid Cancer
Background: Papillary and follicular thyroid cancer were found recently to express somatostatin receptors (SSTRs). 99mTc-depreotide binds with high affinity to SSTRs 2, 3, and 5.
Aim: The aim of this study was to evaluate the feasibility of applying 99mTc-depreotide scintigraphy to search for radioiodine-negative thyroid cancer; comparison is made to a standard approach using 18F-fluorodeoxyglucose-positron emission tomography (18F-FDG-PET).
Patients and Methods: Ten radioiodine-negative patients with suspicion of recurrent or metastatic thyroid cancer were investigated with 99mTc-depreotide scintigraphy and 18F-FDG-PET, performed with a time interval that ranged from 1–8 wk. Locoregional recurrence and metastases were confirmed by ultrasonography and/or computed tomography, together with cytology or histological examination in selected cases.
Results: True-positive results were obtained in nine patients (90%) with 99mTc-depreotide scintigraphy and in seven patients (70%) with 18F-FDG-PET. 99mTc-depreotide scintigraphy gave better results in terms of detection of recurrent or metastatic disease compared with 18F-FDG-PET in three patients, whereas 18F-FDG-PET identified metastatic disease that was not seen with 99mTc-depreotide in only one patient. 99mTc-depreotide scintigraphy portrayed lesions in three patients with negative morphological imaging.
Conclusions: Results indicate a potential value of 99mTc-depreotide scintigraphy for the diagnosis of thyroid cancer in the setting of detectable thyroglobulin and negative radioiodine scan. Furthermore, 99mTc-depreotide adds complementary information regarding the SSTR status of lesions, which may be helpful for individual therapy planning in this group of patients, which is hard to manage clinically.