Abstract
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Purpose: To evaluate the effect of the clinical factors that may influence the diagnostic accuracy of 18F-FDG PET/CT in differentiated thyroid carcinoma (DTC) with elevated thyroglobulin and negative scan (TENIS).
Methods: Relevant studies were identified by searches on PubMed, EMBASE, Web of Science, and Cochrane Library database up to September 2017. Systematic methods were used to select and evaluate the quality of studies. The overall findings of PET studies were extracted and synthesized. Subgroup analyses by inclusion criteria (post diagnostic- vs. therapeutic-whole body scan (131I WBS)), thyroid stimulating hormone condition (under TSH-stimulation vs. -suppression), and patient’s condition when 18F-FDG PET/CT was performed (serum thyroglobin (Tg) >10 ng/mL vs. ≤10 ng/mL, low recurrence risk vs. intermediate-to-high recurrence risk) were carried out
Results: Twenty studies, including 7 retrospective cohort studies, 11 prospective serial observations, and 2 comparative studies were included in this systematic review. The overall patient-based sensitivity and specificity of 18F-FDG PET/CT were 0.881 (95% confidence interval (CI) 0.856-0.907) and 0.878 (95% CI 0.834-0.925), respectively. Subgroup analysis showed no significant difference in sensitivity of PET scans taken under TSH stimulation versus TSH suppression (0.843, 95% CI 0.779-0.912 vs 0.897, 95% CI 0.861-0.934, P=0.377). While statistically significant difference was found in sensitivity of PET scans taken after negative diagnostic 131I WBS versus following negative post-therapeutic 131I WBS (0.829, 95% CI 0.789-0.871 vs 0.852, 95% CI 0.817-0.887, P=0.031). PET scans taken in TENIS patients with Tg > 10 ng/mL versus ≤ 10 ng/mL showed statistically significant differences in the number of patients with PET true-positive lesions, no matter how the Tg value was evaluated, under TSH stimulation (OR=0.413, 95% CI 0.223-0.765, P=0.005) or under TSH suppression (OR=0.460, 95% CI 0.253-0.837, P=0.011). When comparing the number of patients with PET true-positive lesions on 18F-FDG PET scans between TENIS patients with different recurrence risk, no statistically significant difference was detected (OR=0.832, 95% CI 0.509-1.360, P=0.462).
Conclusions: Based on data from recent studies, the application of 18F-FDG PET/CT in TENIS patients should be individualized per their clinical characteristics. 18F-FDG PET/CT seem to have a better performance in patients with post therapeutic negative 131I WBS, and in cases with a Tg value higher than 10 ng/mL.