Dear Sir,
We were very impressed from the outset when reading the paper published by Kirchner et al. recently [1]. It suggested a much higher incidence of detection on positron-emission tomography (PET) scan combined with computed tomography (CT) with fluorodeoxyglucose (FDG) for cancerous and precancerous lesions in the bowel and a greater degree of diagnostic accuracy than had been found in works which did not have the assistance of CT with contrast enhancement and much higher resolution [2,3,4,5,6]. For example, in our own study [7], scans were performed without contrast, and the CT component was acquired with a scanner with 16-slice capability. Would the authors ascribe the discrepancy purely to the difference in CT technology? Or are there other factors found to be of significance?
On further analysis, we found that the positive predictive value (PPV) was similar between the study by Kirchner [1], ours [7], and other studies [2,3,4,5,6] also without the assistance of contrast-enhanced CT. Agress and Cooper [2] and Kamel et al. [3] were omitted as neither the number of incidentally detected colonic lesions nor the proportion followed up was clearly documented (and hence the PPV could not be calculated). The PPV calculated by Gutman et al. [4], Israel et al. [5], Even-Sapir et al. [6], and our study [7] were 61%, 46%, 62%, and 55%, respectively. The PPV cited in their work [1] was 50%. In that case, how much a difference did diagnostic CT really make?
References
Kirchner J, Schaarschmidt BM, Kour F, Sawicki LM, Martin O, Bode J, et al. Incidental 18F-FDG uptake in the colon: value of contrast-enhanced CT correlation with colonoscopic findings. Eur J Nucl Med Mol Imaging. 2019. https://doi.org/10.1007/s00259-019-04579-y.
Agress H Jr, Cooper BZ. Detection of clinically unexpected malignant and premalignant tumors with whole-body FDG PET: histopathologic comparison. Radiology. 2004;230:417–22.
Kamel EM, Thumshirn M, Truninger K, Schiesser M, Fried M, Padberg B, et al. Significance of incidental 18F-FDG accumulations in the gastrointestinal tract in PET/CT: correlation with endoscopic and histopathologic results. J Nucl Med. 2004;45:1804–10.
Gutman F, Alberini J-L, Wartski M, Vilain D, Le Stanc E, Sarandi F, et al. Incidental colonic focal lesions detected by FDG PET/CT. AJR AmJ Roentgenol. 2005;185:495–500.
Israel O, Yefremov N, Bar-Shalom R, Kagana O, Frenkel A, Keidar Z, et al. PET/CT detection of unexpected gastrointestinal foci of 18F-FDG uptake: incidence, localization patterns, and clinical significance. J Nucl Med. 2005;46:758–62.
Even-Sapir E, Lerman H, Gutman M, Lievshitz G, Zuriel L, Polliack A, et al. The presentation of malignant tumours and pre-malignant lesions incidentally found on PET-CT. Eur J Nucl Med Mol Imaging. 2006;33:541–52.
Lee JC, Hartnett GF, Hughes BG, Ravi Kumar AS. The segmental distribution and clinical significance of colorectal fluorodeoxyglucose uptake incidentally detected on PET-CT. Nucl Med Commun. 2009;30:333–7.
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Lee, J.C., Hartnett, G.F. & Ravi Kumar, A.S. The added benefit of contrast-enhanced CT in evaluation of incidental FDG-avid colon lesions. Eur J Nucl Med Mol Imaging 47, 2244 (2020). https://doi.org/10.1007/s00259-020-04716-y
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DOI: https://doi.org/10.1007/s00259-020-04716-y