Prognostic role of FDG PET/CT in patients with differentiated thyroid cancer treated with 131-iodine empiric therapy

Abstract

Background:To assess the long-term prognostic value of 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patients with differentiated thyroid carcinoma (DTC) undergoing empiric radioiodine (RAI) therapy due to raising values of thyroglobulin (Tg).Methods:Forty-nine patients with histological diagnosis of DTC (31 with papillary and 18 with follicular carcinoma) follow-up for a mean period of 7.9 ± 5 years after empiric RAI therapy were retrospectively analyzed.Results:FDG-PET/CT was negative in 15 (30.6%) patients and positive in 34 (69.4%), whereas postradioiodine therapy whole body scan (t-WBS) was negative in 16 (32.7%) and positive in 33 (67.3%) patients. FDG-PET/CT and t-WBS were in agreement in 32 patients (7 both negative and 25 both positive); on the contrary, in 17 patients there was disagreement between FDG-PET/CT and t-WBS (P =ns). At short-term follow-up, Tg normalized in 19 (38.8%) patients and was unchanged or increased in 30 (61.2%). Of the 15 patients with negative FDG-PET/CT, 11 (73.3%) showed Tg normalization, whereas of the 34 patients with positive FDG-PET/CT, only 8 (23.5%) had Tg normalization (χ2 =8.9, P < .005). At multivariate analysis, FDG-PET/CT and Tg normalization at short-term follow-up were independent predictors of disease-free survival (χ2 =26.3, P < .0001), while Tg normalization was the only variable associated with overall survival χ2 =7.2, P < .01).Conclusion:FDG-PET/CT in association with Tg normalization at short-term follow-up may be useful for long-term prognostic stratification in DTC patients.

Investigating 18F-FDG PET/CT Parameters as Prognostic Markers for Differentiated Thyroid Cancer: A Systematic Review

“…Ultimately, 25 studies ( 14 – 38 ) were included in this systematic review ( Figure 1 ). Thirteen (52.0%) studies ( 16 – 20 , 22 , 23 , 25 , 26 , 31 , 32 , 35 , 37 ) were assessed as “unclear” for the domain of study participation, mostly due to a lack of information about the source population and the population of interest (TNM stage, histology, etc. ), or ambiguous inclusion and exclusion criteria.…”

“…The common indications of PET/CT before radioactive iodine (131-I) therapy included an elevated Tg, abnormal imaging (WBS, US, and CT), high-risk histopathology, and suspicion or proven metastases. Four studies did not report the indication ( 20 – 22 , 34 ).…”

Efficacy of Empirical Radioiodine Therapy in Patients with Differentiated Thyroid Cancer and Elevated Serum Thyroglobulin without Evidence of Structural Disease: A Propensity Score Analysis

“…Of note, among the eight patients with lung metastases, only four underwent further RAI treatment during the subsequent follow-up. It should be considered that PET/CT imaging emerged has a strong complementary tool for the evaluation of patients with suspected DTC recurrence [ 22 , 23 , 24 , 25 ]. In our population, PET/CT has not been routinely performed in all patients; it should be considered that additional imaging findings would have had an impact on the selection of candidate patients for RAI treatment.…”

Impact of FDG-PET on therapy management and outcome of differentiated thyroid carcinoma patients with elevated thyroglobulin despite negative iodine scintigraphy

“…Previous studies regarding FDG-PET and outcome in DTC patients could only elaborate on the prognostic value of the imaging modality, i. e. that positive results on PET scans correlate with shorter survival times [13,14,19,25,29,31] whereas negative scans have high negative predictive value for adverse events due to DTC [3,22,28]. The primary aim of our study was to assess whether FDG-PET imaging improves survival of DTC patients with suspected dedifferentiation.…”