Thyroglobulin doubling time offers a better threshold than thyroglobulin level for selecting optimal candidates to undergo localizing [18F]FDG PET/CT in non-iodine avid differentiated thyroid carcinoma

Abstract

Purpose To investigate the potential role of serum thyroglobulin doubling time (TgDT) in predicting 2-deoxy-2-[ 18 F]fluoro-Dglucose ([ 18 F]FDG) PET/CT results in patients affected by differentiated thyroid carcinoma (DTC) who demonstrated a combination of positive Tg but a negative [ 131 I] whole-body scan ([ 131 I]-WBS). Materials and methods Inclusion criteria were (1) prior [ 131 I] treatment for DTC, (2) negative subsequent [ 131 I]-WBS, (3) no interfering anti-Tg antibodies, (4) three consecutive Tg measurements under the thyroid hormone replacement therapy to calculate TgDT before 2-[ 18 F]FDG PET/CT, and (5) at least 6 months of clinical and/or imaging follow-up to ascertain the diagnosis. Receiver operating characteristic (ROC) curve and the area under the curve (AUC) were used to identify the optimal cutoff point for the last stimulated Tg and TgDT prior to [ 18 F]FDG PET/CT. Results One hundred and thirteen patients were included. Seventy-four (65%) patients had positive [ 18 F]FDG PET/CT for DTC recurrence, while the remaining 39 (35%) negative. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of [ 18 F]FDG PET/CT were 92%, 94%, 97%, 87%, and 93%. Patients with positive [ 18 F]FDG PET/CT had higher Tg and TgDT than those with negative PET/CT. ROC curve analysis revealed an optimal Tg cutoff of 19 ng/mL (sensitivity 78%, specificity 85%, AUC = 0.844) and TgDT of 2.5 years (sensitivity 93%, specificity 87%, AUC = 0.911). TgDT threshold of 2.5 years predicted significantly (p = 0.023) better than Tg level PET/CT results. Conclusions The diagnostic performance of [ 18 F]FDG PET/CT could be significantly improved when TgDT is less than or equal to 2.5 years, as compared with using the absolute Tg level. Keywords Thyroglobulin doubling time. Differentiated thyroid carcinoma. Thyroglobulin. [ 18 F]FDG PET/CT. Diagnostic test performance This article is part of the Topical Collection on Endocrinology

The role of Tg kinetics in predicting 2-[18F]-FDG PET/CT results and overall survival in patients affected by differentiated thyroid carcinoma with detectable Tg and negative 131I-scan

“…The hypothesis of a connection between Tg kinetics and PET detection rate is logical and based on the idea that an aggressive and rapidly growing tumor should have a greater metabolic activity and is more likely to be FDG-avid. The effective usefulness of Tg kinetics in predicting PET/CT results is not completely understood with promising papers [21,22]. Giovanella et al [21] demonstrated that the accuracy of 2-[ 18 F]-FDG PET/CT was significantly higher in patients with unstimulated Tg above 5.5 ng/mL and the TgDT below 1 year.…”

“…Giovanella et al [21] demonstrated that the accuracy of 2-[ 18 F]-FDG PET/CT was significantly higher in patients with unstimulated Tg above 5.5 ng/mL and the TgDT below 1 year. A recent study [22] showed the superiority of TgDT using a threshold of 2.5 years compared to Tg as absolute value.…”

“…Finally we recruited 139 DTC patients [F = 64, M = 75, median age 56 years, range: 20-82 years; male to female ratio = 1.2:1] who underwent 2-[ 18 F]-FDG PET/CT with last post therapeutic [ 131 I]WBS negative and detectable Tg (≥1 ng/mL) without detectable Tg-antibodies and Tg in increasing. There was a partial overlap (n 80) of patients included with a previous paper of the same center [22].…”

“…Few studies suggested a prognostic role of post-ablation Tg-doubling time (TgDT) in predicting survival outcome [14][15][16][17][18][19][20], while only two papers demonstrated [21,22] that TgDT was an independent factor to predict 2-[ 18 F]-FDG PET/CT results.…”

A Stepwise Approach Using Metastatic Lymph Node Ratio-Combined Thyroglobulin for Customization of [18F]FDG-PET/CT Indication to Detect Persistent Disease in Patients with Papillary Thyroid Cancer

“…To identify an [ 18 F]FDG-PET/CT indication for PD detection, serum Tg level before RAI therapy is a well-established parameter [ 19 , 20 ]. In a recent study, the diagnostic performance of PET/CT for PRD detection was significantly improved by Tg doubling time with an optimal threshold of 2.5 years in DTC patients with negative IWBS findings [ 21 ]. However, serum Tg levels could be influenced by several factors such as serum TgAb level and TSH stimulation methods [ 22 ].…”