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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 9 of 13

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Figure 6. Summary receiver operating characteristic curve for detection of hematogenous metastases by F-FDG PET/CT in the patient-
based analysis.

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For lung lesions, it was possible to compare the DR of F-FDG PECT/CT with that of CT. As expected,
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CT did not perform inferiorly compared to F-FDG PECT/CT. Nevertheless, F-FDG PECT/CT proved
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superior to MRI in this setting (95.02% vs. 64.93%). The sensitivity of PECT/CT in the detection of lung
metastases, with corresponding TP and FN cases, was reported in only 2 studies by Vrachimis (100%, 52
[24]
[33]
[34]
lung metastases ; 100%, 68 lung metastases ). Nakajo et al. reported in their study that FN lung lesions
at FDG PET imaging were significantly smaller than TP lung lesions (mean size = 3.8 ± 2.1 mm vs. 9.5 ± 6.2 mm;
P = 0.001).
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When assessing the diagnostic AC of F-FDG PECT/CT, it appeared clear that a further advantage of
18 F-FDG PECT/CT in the detection of hematogenous metastases is its very high specificity (95.6% on a per-
patient basis and 93.4% on a per-lesion basis). Unfortunately, due to the available literature, no comparison
with the diagnostic AC of other imaging techniques was possible. In addition, for the diagnostic AC, the
substantial heterogeneity of findings is attributable mainly to the small samples of the studies.

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The diagnostic performance of I-WBS (planar) was consistently reported lower compared to F-FDG
[23]
PECT/CT in the detection of hematogenous metastases. Indeed, the study of Nagamachi et al. showed
131
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a lower DR for I-WBS compared to F-FDG PECT/CT (71.43% vs. 85.71%); similarly, the performance
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131
of I-WBS has proved substantially inferior to that of F-FDG PECT/CT in the detection of lung
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metastases [22,23] . Differently, I-WBS SPECT/CT may provide a gain in the detection of bone metastases
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compared to planar imaging. Indeed, in the study of Qiu et al. , the accuracy of I-WBS SPECT/CT
[29]
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was 93.92%, whereas the accuracy of F-FDG PECT/CT was 86.49%. Unfortunately, no other study in