18F-FDG PET/CT concurrent with first radioiodine post-therapeutic scan in high risk differentiated thyroid cancer: a useful tool or just an expensive diversion?

Autor: Alessio RIZZO, Germano PEROTTI, Luca ZAGARIA, Valerio LANNI, Manuela RACCA, Nicola PALESTINI, Massimo SALVATORI
Rok vydání: 2023
Předmět:
Zdroj: The Quarterly Journal of Nuclear Medicine and Molecular Imaging. 67
ISSN: 1827-1936
1824-4785
DOI: 10.23736/s1824-4785.22.03364-7
Popis: Aim of the present study was to evaluate the clinical impact of fluorine-18F-fluorodeoxyglucose PET/CT (18F-FDG-PET/CT) concurrent with post-therapeutic whole-body radioiodine scan (TxWBS) after first radioiodine (RAI) treatment in patients with high-risk differentiated thyroid carcinoma (DTC).This was a retrospective, single-centre study including 39 patients with DTC (22 females, 17 males, median age 54; IQR 35-60 years, 87 % papillary thyroid cancer, 13 % follicular thyroid cancer). All patients underwent 18F-FDG-PET/CT and RAI treatment, both performed off LT4 about 3 months after total thyroidectomy. TxWBS was obtained 3 days afterwards using planar technique and SPECT/CT of neck and thorax regions. Semi-quantitative analysis was performed on positive 18F-FDG-PET/CT scans to assess SUVMax, SUVRatio, MTV and TLG values in target lesions (hottest 18F-FDG-positive lesion present in each patient). Receiver operating characteristics (ROC) curve analysis was obtained to establish a cut-off point for SUVMax able to predict the presence of RAI nonavid lesions. Univariate and multivariate analyses were executed to find out predictive factors for abnormal 18F-FDG-PET/CT imaging.In 11 (28%) patients 18F-FDG-PET/CT and TxWBS were both negative and in 9 (23%) both positive, showing loco-regional or distant metastases. In 14 patients (36%) 18F-FDG-PET/CT showed more lesions than TxWBS, while in 5 (13%) patients more lesions were present at TxWBS than 18F-FDG-PET/CT. Overall, 23 patients (59%) showed 18F-FDG avid lesions and 18F-FDG-PET/TC changed the management in 14 (36%), including the choice to perform RAI therapy with higher activities than expected, lymph-node dissection for loco-regional metastases, direct therapy for solitary bone metastases. Through ROC curve analysis, a value superior to 7,25 of SUVMax was able to predict the presence of RAI non-avid lesion at TxWBS. Serum stimulated thyroglobulin and extra-nodal invasion resulted to be risk factors for abnormal 18F-FDG-PET/CT imaging. However, only extra-nodal invasion turned out to be an independent risk factor for abnormal 18F-FDG-PET/CT.The present study demonstrated the clinical value of RAI-concurrent 18F-FDG-PET/CT in patients with high-risk DTC. However, some questions remain open, including the pre-therapeutic thyroglobulin level to use as indication to 18F-FDG-PET/CT and the predictive value of 18F-FDG-PET/CT semi-quantitative parameters.
Databáze: OpenAIRE
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