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Quartuccio et al. J Cancer Metastasis Treat 2021;7:14 I http://dx.doi.org/10.20517/2394-4722.2020.118 Page 11 of 13

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Other investigated imaging techniques that have been compared to F-FDG PECT/CT for the detection of
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hematogenous metastases include F-FDG PET/MRI and PET imaging with Ga DOTA derivatives [20,33,34] .
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[20]
In the study of Klain et al. , the use of F-FDG PET/MRI did not result in additional benefit in the
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assessment of lung metastases, obtaining a lower SS (87.5%) compared to F-FDG PET/CT (93.75%) and
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MRI (100%). Likewise, F-FDG PET/MRI was outperformed by F-FDG PET/CT in the detection of lung
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[33]
[34]
metastases in the study of Vrachimis et al. (AC: 79.01% vs. 97.53%) . According to the limited available
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literature, the use of Ga DOTA derivatives does not seem to provide noticeable advantages in terms of
diagnostic accuracy for lung lesions.
Our meta-analysis presented some limitations. The selected studies provided small sample sizes. Due to
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the mixed population of most studies, a subgroup analysis of the performance of F-FDG PET/CT based
on the histological type was not possible. We also noticed the impossibility to extract accurate data on the
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diagnostic performance of F-FDG PET/CT for subjects with unelevated Tg and/or positive I-WBS from
the included studies in the present meta-analysis; it is conceivable that the diagnostic performance of PET/
CT would be inferior for this subgroup of patients compared to the general population.
A source of bias may derive from the substantially high heterogeneity of findings across the studies. Further
sources of bias may arise from methodological differences across the studies, including the type of PET/CT
scanner. Given the wide range of publication date (2007-2020), studies used PET scanners with different
scintillating crystals and reconstruction methods. Furthermore, we noticed that no study using PET/CT
scanners equipped with a solid-state detector was found in our meta-analysis. It would be interesting in the
future to assess whether these PET/CT scanners may provide a better diagnostic performance in detecting
metastases in patients with advanced DTC.

CONCLUSION
The present meta-analysis suggests the use of F-FDG PECT/CT for the identification of hematogenous
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metastases in patients with thyroid cancer. Nevertheless, the limited number of available studies urges
further research in this setting. Comparative studies are still needed to clarify the performance of F-FDG
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against other radiotracers and imaging techniques. Furthermore, studies evaluating the impact of
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diagnostic performance of F-FDG PET/CT on patient management are warranted.

DECLARATIONS
Authors’ contributions
Performed data search, statistical analysis and wrote the first draft of the manuscript: Quartuccio N.
Made substantial contributions to conception and design of the study and revision: Rubello D.
Provided technical and editing support: Rubello D.

Availability of data and materials
Not applicable.

Financial support and sponsorship
None.

Conflicts of interest
All authors declared that there are no conflicts of interest.

Ethical approval and consent to participate
Not applicable.