Iranian Journal of Nuclear Medicine

Iranian Journal of Nuclear Medicine

[⁶⁸Ga]Ga-DOTATATE vs. [¹⁸F]FDG PET/CT in radioiodine-refractory differentiated thyroid cancer: An exploratory pilot study of uptake patterns and potential implications for peptide receptor radionuclide therapy

Articles in Press

Document Type : Original Article

Authors
Alireza Emami-Ardekani 1
Masoumeh Pourghayoomi 2
Mehrshad Abbasi 2
Saeed Farzanehfar 2
Peyman Sheikhzadeh 2, 1
Nasim Vahidfar 2
Yalda Salehi 2
1 Research Center for Nuclear Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran
2 Department of Nuclear Medicine, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran
10.22034/irjnm.2026.130598.1773
Abstract
Introduction: Patients with radioiodine-refractory differentiated thyroid carcinoma (RAIR-DTC) may require alternative therapeutic approaches. This study aimed to characterize somatostatin receptor uptake using [⁶⁸Ga]Ga-DOTATATE PET/CT, compare the findings with [¹⁸F]FDG PET/CT, and explore potential implications for peptide receptor radionuclide therapy (PRRT).
Methods: This exploratory pilot study included 10 patients with RAIR-DTC who had undergone [¹⁸F]FDG PET/CT within the preceding two months. [⁶⁸Ga]Ga-DOTATATE PET/CT was performed approximately 60 minutes after intravenous administration of 3–7 mCi of the radiotracer. Uptake parameters were compared between the two modalities, and potential imaging-based suitability for PRRT was evaluated using an adapted modified Krenning scoring system.
Results: No statistically significant differences in lesion SUVmax were observed between the two modalities across the evaluated anatomical sites. In pulmonary metastases, [¹⁸F]FDG uptake was numerically higher than [⁶⁸Ga]Ga-DOTATATE uptake (median SUVmax: 4.1 vs. 1.7; p = 0.069). Blood-pool SUVmax was significantly lower with [⁶⁸Ga]Ga-DOTATATE than with [¹⁸F]FDG (p = 0.005). Based on dominant lesion uptake, nine patients had modified Krenning scores of 0–1, while one patient had a score of 2. No patient demonstrated a score of 3 or 4.
Conclusion: In this exploratory pilot study, [⁶⁸Ga]Ga-DOTATATE uptake was generally low and heterogeneous in patients with RAIR-DTC. Most patients did not meet conventional imaging thresholds considered favorable for PRRT in neuroendocrine tumors. However, these criteria have not been validated in RAIR-DTC, and the findings cannot establish ineligibility or lack of therapeutic benefit. Larger prospective studies are needed to clarify the role of SSTR imaging in this population.
Keywords
Radioiodine-refractory differentiated thyroid carcinoma
[⁶⁸Ga]Ga-DOTATATE
[¹⁸F]FDG PET/CT
Somatostatin receptor imaging
Peptide receptor radionuclide therapy
Subjects
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Iranian Journal of Nuclear Medicine

Articles in Press, Accepted Manuscript
Available Online from 02 November 2026