Gastrointestinal 18F-FDG uptake in PET/CT without corresponding morphological mass: Early predictor of cancer development?

Objectives Gastrointestinal (GIT) FDG uptake can frequently be found on FDG-PET/CT even in patients without known GIT malignancy. Aim was to evaluate whether increased GIT FDG uptake without correlate on CT is able to early identify patients developing GIT malignancies.

Methods The esophagogastric junction, the gastric wall, the wall of the rectal ampulla, and the anal canal were evaluated for increased FDG uptake in 1006 patients without known GIT malignancies. Patients without qualitatively elevated FDG uptake were assigned to group A, patients with qualitatively elevated FDG uptake to group B. Differences between the SUVmax of groups A and B were tested for significance using the Mann-Whitney-Wilcoxon’s test (p<0.05). A clinical and radiological follow-up of at least one year (mean: 853+/-414 d) served as the standard of reference to detect tumor development.

Results 460 patients had to be excluded based on insufficient follow-up data. For the remaining 546 patients results were as follows: Gastroesophageal junction: mean SUVmax of group A: 3.1+/-0.66, of group B: 4.0+/-1.11, p<0.01. Gastric wall: mean SUVmax of group A: 2.8+/-0.77, of group B: 4.1+/-1.33, p<0.01. Rectal ampulla: mean SUVmax of group A: 2.8+/-0.83, of group B: 3.9+/-1.49, p<0.01. Anal canal: mean SUVmax of group A: 2.7+/-0.55, of group B: 3.9+/-1.59, p<0.01. One patient developed gastric cancer on follow-up.

Conclusions Elevated esophagogastric or anorectal FDG uptake does not predict cancer development if the corresponding CT is unremarkable. With unremarkable CT further investigation of increased GIT FDG-uptake does not seem to be necessary.