High level of agreement established between pre-therapeutic 124I-PET and intra-therapeutic 131I-imaging to detect iodine-positive Thyroid Cancer metastases

In the newest issue of Journal of Nuclear Medicine, Dr. Marcus Ruhlmann from the University Duisburg-Essen and colleagues report the results of their retrospective study to establish the level of agreement between 124I-PET and 131I-imaging in the detection of iodine-positive metastases in patients with differentiated Thyroid Carcinoma [1].

In this study, 137 patients (with a total of 227 metastases that appeared iodine-positive in both imaging methods) underwent PET/CT 24 h and 120 h after administration of 124I in diagnostic amounts, followed by whole-body scintigraphy and SPECT/CT scan of the neck 5 to 10 days after injection of 131I in therapeutic amounts.
In the lesion-based analysis, the level of agreement between 124I-PET and 131I-imaging was 97% (221/227 lesions); 124I-PET detected 98% (223/227) and 131I-imaging 99% (225/227) of the iodine-positive metastases. In the analysis of patients with iodine-positive metastases (61/137 subjects), the level of agreement was 95% (58/61); 124I-PET detected at least one iodine-positive metastasis in 97% (59/61) and 131I-imaging in 98% (60/61) of the patients. Both modalities showed congruence in the identification of patients without pathologic iodine uptake (76/137 subjects).
Considering the high level of agreement obtained between 124I-PET and 131I-imaging, the authors conclude that pre-therapeutic 124I-PET/CT is a suitable procedure to detect iodine-positive metastases in patients with differentiated Thyroid Carcinoma. Moreover, it can be employed as a reliable tool for both staging of thyroid cancer patients as well as individualized treatment planning.

[1] Ruhlmann M, Jentzen W, Ruhlmann V, Pettinato C, Rossi G, Binse I, Bockisch A, Rosenbaum-Krumme S (2016). High Level of Agreement Between Pretherapeutic 124I PET and Intratherapeutic 131I Imaging in Detecting Iodine-Positive Thyroid Cancer Metastases. J Nucl Med 57 (9): 1339-1342. PMID: 27151981

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