Focal colorectal uptake in (18)FDG-PET/CT: maximum standard uptake value as a trigger in a semi-automated screening setting.

BACKGROUND: Focal colorectal uptake in (18)FDG-PET/CT may be associated with a malignancy and can be quantified. This provides the basis for an automatic trigger threshold above which cases are flagged for colonoscopic evaluation and below which for individual assessment.

PURPOSE: To determine the lowest maximum standard uptake (SUVmax) in colorectal cancer that could be used as a threshold to trigger endoscopic evaluation and to evaluate whether the SUVmax needs to be further normalised to a priori known extrinsic factors.

METHODS: The SUVmax was measured in 54 colorectal carcinomas and correlated with gender, age, blood glucose level, injected activity, body mass index and time to scan using t test or correlation coefficients (Pearson or Spearman, according to distribution).

RESULTS: There was no correlation between SUVmax and any of the extrinsic factors mentioned above. The lowest SUVmax value was 5 [mean ± SD (range): 11.1 ± 4.8 (5.0-24.6)].

CONCLUSION: In contrast to most other screening techniques, semi-automation in colorectal screening seems possible with PET/CT. This opens the door for further study into the feasibility of automated screening. Independent from extrinsic factors, an SUVmax ≥5.0 in a focal colorectal uptake in (18)FDG-PET/CT should automatically trigger for endoscopic evaluation, if not contraindicated. Cases with SUVmax <5 should be assessed individually before referral for endoscopy. Thus, more interpretation time could be spent on those cases with a lower uptake and more ambiguous diagnosis.