Colorectal cancer screening in asymptomatic adults: the role of FDG PET scan.

The aim of this study was to evaluate the potential application of 18F-fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) for colorectal cancer screening in asymptomatic individuals. The subjects consisted of 3210 physical check-up examinees (1736 men, 1474 women; mean age +/- SD, 53.2 +/- 8 y) with non-specific medical history. In the control group, 12 patients who had gastrointestinal symptoms with biopsy-proved colon carcinoma were recruited. Whole-body FDG PET was performed on all patients. Focal hypermetabolic areas with an intensity equal to or exceeding the level of FDG uptake in the brain and bladder were considered abnormal and interpreted as intraluminal neoplasia. Among the 3210 FDG PET examinations, advanced neoplasm was present in 20 examinations, including 2 tubular adenomas larger than 1 cm, 12 villous adenomas and 6 cancers. Of 6 examinees diagnosed with cancer, one had a Dukes stage A lesion, four had Dukes stage B lesion and one had a Dukes stage C lesion. In the control group, of 12 patients with biopsy-proved carcinoma followed by FDG PET scan, six had a Dukes stage B lesion, four had Dukes stage C lesion and two had a Dukes stage D lesion. The mean and standard deviation of standard uptake value (SUV) in colonic adenoma and carcinoma is 3.56 +/- 0.68 and 5.74 +/- 2.26, respectively. The sensitivity of using FDG PET in the detection of primary colorectal cancer is high. Primary colorectal cancer can be detected with FDG PET in a resectable stage. FDG PET could detect large size (> 0.7 cm) and pre-malignant change of colonic adenoma. It is possible to differentiate adenoma from carcinoma of colon by an increased rate of glycolysis (SUV) in carcinoma.