Lesion Location in Clinical Significance of Incidental Colorectal FDG Uptake

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Clin Endosc. 2012;45(4):451-452
Publication date (electronic) : 2012 November 30
doi : https://doi.org/10.5946/ce.2012.45.4.451
1Department of Nuclear Medicine, The Prince Charles Hospital, Chermside, Australia.
2University of Queensland School of Medicine, Herston, Australia.
3Department of Medical Oncology, Redcliffe General Hospital, Redcliffe, Australia.
4Department of Nuclear Medicine and Queensland PET Service, Royal Brisbane and Women's Hospital, Herston, Australia.
Correspondence: Joseph C. Lee, Department of Nuclear Medicine, The Prince Charles Hospital, Rode Road, Chermside, Qld 4032, Australia. Tel: +61-7-3139-4000, Fax: +61-7-3139-4860, Joseph_Lee@health.qld.gov.au

To the Editor

We agree with Roh et al.1 that cancerous and pre-cancerous lesions may be harboured by the finding of incidental F-18-fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET) scan. This study-and our own data2-advocates for urgent investigation of such findings, especially considering the treatment implications for patients undergoing therapy for other established malignancies (which was the principal indication for PET).

With regard to measurement of maximum standardised uptake values (SUVmax)-favoured to a greater extent in the accompanying editorial commentary3-we found in our study (and in our clinical work in general) that it was not adequately useful in assessing malignancy likelihood. We, too, found the degree of overlap in the range of values was often confounding. While utilising imaging clues to predict malignancy potential is very useful, SUVmax seemed not to be as helpful as we initially hoped.

In our experience, focal FDG uptake is much more concerning for significant pathology than segmental or diffuse FDG uptake, regardless of the SUVmax value. We also found that anatomical location (with lesions classified as simply as being in the "proximal" or "distal" colon) had a higher predictive value for malignancy. It is also important to note that other studies of this phenomenon have found that as many as 17%4 to 32%5 of foci of abnormal colonic FDG uptake represented aetiologies other than malignancy.

Indeed, recent publications suggest that some of this uptake may be related to bacterial labelling in the colonic lumen.6 More work is required to elucidate the pathophysiology and possible causes of FDG uptake in the colon. Regardless, based on study of Roh et al.1 and our own,2 consideration should always be given to investigating focally increased colonic FDG uptake to exclude neoplasia. Additional clues in establishing the clinical significance are also potentially very helpful.

Notes

The authors have no financial conflicts of interest.

References

1. Roh SH, Jung SA, Kim SE, et al. The clinical meaning of benign colon uptake in 18F-FDG PET: comparison with colonoscopic findings. Clin Endosc 2012;45:145–150. 22866255.
2. 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;30:333–337. 19262416.
3. Jang BI. Benign colonic 18F-FDG uptake on whole-body FDG-PET scan. Clin Endosc 2012;45:109–110. 22866246.
4. Israel O, Yefremov N, Bar-Shalom R, et al. PET/CT detection of unexpected gastrointestinal foci of 18F-FDG uptake: incidence, localization patterns, and clinical significance. J Nucl Med 2005;46:758–762. 15872347.
5. Kamel EM, Thumshirn M, Truninger K, 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;45:1804–1810. 15534047.
6. Wang K, Chen YC, Palmer MR, et al. Focal physiologic fluorodeoxyglucose activity in the gastrointestinal tract is located within the colonic lumen. Nucl Med Commun 2012;33:641–647. 22240934.

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