Presence of a focal colonic FDG uptake incidental finding on a PET/CT scan justifies a colonoscopy to detect (pre-)malignant lesions. The fusion of PET and CT images allows an accurate localization of the lesions. PET/CT is a useful tool to differentiate pathologic from physiologic FDG uptake.

This prospective study aimed to compare the diagnostic performance of 18 F-fluorocholine and 18 F-FDG for detecting and staging hepatocellular carcinoma (HCC) in patients with chronic liver disease and suspected liver nodules. Methods: Whole-body PET/CT was performed in a random order at 10 min after injection of 4 MBq of 18 F-fluorocholine per kilogram and at 1 h after injection of 5 MBq of 18 F-FDG per kilogram. PET/CT results were read in a masked manner by 2 specialists, and diagnostic performance was assessed from the results of consensus masked reading. Those focal lesions appearing with increased or decreased activity, compared with background, on 18 F-fluorocholine PET/CT were considered positive for malignancy. The standard of truth was determined on a per-site basis using data from a histologic examination and a follow-up period of more than 6 mo; on a per-patient basis, the Barcelona criteria were also accepted as a proof of HCC in 5 patients. Results: Eighty-one patients were recruited; standard of truth was determined in 59 cases. HCC was diagnosed in 34 patients. Therefore, sensitivity was 88% for 18 F-fluorocholine and 68% for 18 F-FDG (P 5 0.07), and in 70 sites, sensitivity was 84% for 18 F-fluorocholine, significantly better than the 67% for 18 F-FDG (P 5 0.01). Of the 11 patients with well-differentiated HCC, 6 had a positive result with 18 F-fluorocholine alone, whereas 18 F-FDG was never positive alone; corresponding site-based sensitivity was 94% for 18 F-fluorocholine and 59% for 18 F-FDG (P 5 0.001). The detection rate of 18 sites corresponding to other malignancies was 78% for 18 F-fluorocholine and 89% for 18 F-FDG. In nonmalignant sites, 18 F-fluorocholine appeared less specific than 18 F-FDG (62% vs. 91% P , 0.01) because of uptake by focal nodular hyperplasia. Conclusion: 18 F-fluorocholine was significantly more sensitive than 18 F-FDG at detecting HCC, in particular in well-differentiated forms. In contrast, 18 F-FDG appeared somewhat more sensitive at detecting other malignancies and was negative in focal nodular hyperplasia. Thus 18 F-fluorocholine appears to be a useful PET/CT tracer for the detection and surveillance of HCC; however, performing PET/CT with both radiopharmaceuticals seems to be the best option.

FCH provides a high detection rate for HCC, making it potentially useful in the initial evaluation of HCC or in the detection of recurrent disease. The favourable result of this proof-of-concept study opens the way to a phase III prospective study.