Evaluation of 18F-FDG PET imaging in post-therapeutic patients with gastric malignancy

Objective: To evaluate the usefulness of 18F-fluorodeoxyglucose (FDG) PET imaging in post-therapeutic patients with gastric malignancy. Methods: 52 post-therapeutic patients with gastric malignancy underwent 18F-FDG PET imaging. CT imaging was performed in 49 patients within 30 d of the PET study. Results of 18F-FDG PET imaging were verified by histopathology or clinical follow-up and other imaging examination. Results: 1) 23 patients showed regional 18F-FDG uptake in gastric site. The hypermetabolic foci were proved to be recurrent or residual tumors [standardized uptake value (SUV) 4.24 ± 2.98] in 9 patients and benign including physiological, inflammatory or abnormal gastric motility uptake (SUV 2.72 ± 0.62) in 14 patients. There was significant difference between them (P<0.05). 2) The sensitivity of PET imaging for detecting metastatic lesions was 90.0% (27/30), and that of CT was 50.0% (15/30). For metastatic lesions, PET imaging was concordant with CT in 9 patients, found more lesions than CT in 6 patients, and detected lesions in 10 patients while CT was negative. In 2 patients PET imaging rules out lesions suspected by CT but found lesions in other sites. PET imaging also detected metastases in 5 patients with slightly elevated tumor marker and no positive findings by other imaging modalities. In 25 PET imaging negative patients there were 3 false negatives. Conclusions: PET imaging has high sensitivity but low specificity for detecting residual or recurrent lesions in patients with gastric malignancy after therapy. However, PET is more useful in finding metastatic lesions than CT. (authors)