Head-to-head comparison of F-18 FDG PET/CT in radioidine refractory thyroid cancer patients with elevated versus suppressed TSH levels a pilot study

Abstract

Introduction: To perform a head-to-head comparison of the uptake pattern of F-18 fluorodeoxyglucose in positron emission computed tomography (FDG PET/CT) in radioiodine refractory thyroid carcinomas (RAIR) in the same patient under elevated TSH levels (eTSH) and suppressed TSH levels (sTSH). Methods: FDG PET/CT studies were performed under two conditions: levothyroxine intake (sTSH) and 30 days after hormonal withdrawal (eTSH). SUVmax values and the number of lesions detected (local recurrence and metastases in cervical and distant lymph nodes, lungs and bone) where blindly evaluated. Blood serum TSH and Tg levels were obtained prior to both studies. FDG PET/CT imaging, neck ultrasound, biopsy and follow-up were considered the reference standard. Results: Fifteen patients performed both eTSH and sTSH FDG PET/CT studies. Both were positive for metastases in 80% of the patients. eTSH FDG PET/CT studies did not reveal increased uptake (p ¼ 0.0640) and did not demonstrate a higher number of lesions (p ¼ 0.320) when compared to sTSH FDG PET/CT studies. There was no change in the clinical management of these patients. Conclusions: eTSH FDG PET/CT in patients with RAIR did not show more metastases in comparison to sTSH FDG PET/CT and there was no impact in clinical management of patients. Elevating TSH levels (whether by hormonal withdrawal or recombinant TSH) in patients being submitted to FDG PET/CT may not be necessary.

2-[18F]FDG PET in the Management of Radioiodine Refractory Differentiated Thyroid Cancer in the Era of Thyrosin-Kinases Inhibitors: A Real-Life Retrospective Study

“…In their recent prospective analysis, Almeida LS et al failed to find a significant difference in SUVmax and in diagnostic accuracy of 2-[ 18 F]FDGPET/CT performed during TSH stimulation in hormonal withdrawal compared to those in TSH-suppression. However, in this case, the study population was very small, and the correlation between TSH and SUVmax almost reached the statistical significance ( p = 0.064) [ 26 ]. Furthermore, the previous meta-analysis published in 2010 by Ma et al stated the role of TSH stimulation in improving diagnostic performance of 2-[ 18 F]FDGPET in patients treated for a RR-DTC, with elevated Tg levels and a negative whole-body scintigraphy (WBS) scan [ 27 ].…”