Objective To systematically evaluate the diagnostic efficacy of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT in differentiated thyroid cancer (DTC) recurrence patients with positive expression for thyroglobulin (Tg) (referred as Tg-positive) and negative result for ¹³¹I whole body imaging (WBS) (referred as ¹³¹I-WBS-negative).

Methods PubMed, Embase, Cochrane Library, Wanfang Data Knowledge Service Platform, China National Knowledge Internet, VIP Database, and China Biomedical Literature Database were searched for relevant studies on the diagnosis of DTC recurrence by ¹⁸F-FDG PET/CT. The search time was from database establishment to December 2020. The literature was screened according to the inclusion and exclusion criteria, the basic characteristics and diagnostic parameters of the studies were extracted. Spearman correlation coefficient was used to analyze whether there was a threshold effect in the literature. Heterogeneity Q test was performed for the included literature, and Deeks linear regression analysis was used to evaluate the publication bias of the literature. The summary receiver operetor characteristic (SROC) curve was drawn, the area under the curve (AUC) was calculated, and the Z test was used to analyze the difference in the diagnostic performance of ¹⁸F-FDG in patients undergoing diagnostic whole-body imaging (Dx-WBS) and therapeutic imaging (Rx-WBS). The differences in the diagnostic performance of ¹⁸F-FDG PET/CT between thyroid-stimulating hormone (TSH)-stimulated and suppressed states were also analyzed.

Results Finally, 16 articles were included, with a total of 1 036 patients with DTC recurrence. The heterogeneity of the included studies was low (I²=47.5%, P=0.018), which may be due to the number of cases (r=1.462, P=0.021), and there was a small publication bias (P=0.070). The combined sensitivity of ¹⁸F-FDG PET/CT in diagnosing Tg-positive and ¹³¹I-WBS-negative DTC recurrence patients was 0.87(95%CI: 0.82−0.91), the specificity was 0.79(95%CI: 0.68−0.86), and the positive likelihood ratio was 3.76(95%CI: 2.32−6.09), the negative likelihood ratio was 0.20(95%CI: 0.14−0.27), the diagnostic odds ratio was 23.89(95%CI: 13.23−43.12), and the AUC of SROC=0.905 (standard error of 0.022) and Q-index was 0.837 (standard error of 0.023). There was no significant difference in the diagnostic performance of ¹⁸F-FDG PET/CT between patients undergoing Dx-WBS and Rx-WBS (Z=0.041, P>0.05); there was no significant difference in the diagnostic performance of ¹⁸F-FDG PET/CT between TSH-stimulated and suppressed states undergoing Dx-WBS and Rx-WBS (Z=1.864, 0.525; both P>0.05).

Conclusions ¹⁸F-FDG PET/CT has high diagnostic efficacy for Tg-positive and ¹³¹I-WBS-negative DTC recurrence patients. The diagnostic efficacy of ¹⁸F-FDG PET/CT in patients undergoing Dx-WBS and Rx-WBS, in TSH-stimulated and suppressed states is similar.