Lesion Location in Clinical Significance of Incidental Colorectal FDG Uptake

We agree with Roh et al.1 that cancerous and pre-cancerous lesions may be harboured by the finding of incidental F18-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 alClin Endosc 2012;45:451-452