Clinical significance of performing ¹⁸F-FDG PET on patients with gastrointestinal stromal tumors: A summary of a Japanese multicenter study

Objective: The aim of this study is to evaluate the clinical significance of performing ¹⁸F-fluorodeoxyglucose (FDG) positron-emission tomography (PET) on patients with gastrointestinal stromal tumors (GISTs). Methods: The patient samples for this study were provided by seven PET institutions in Japan. Forty-one patients with pathologically proved GISTs, 24 men and 17 women (mean age 60.3 years, range 26-81 years) were enrolled in this study. Final diagnosis was based on the follow-up imaging at least 3 months after the PET scan or histopathological examinations. Results: There were eight preoperative cases and 33 follow-up cases in our series. Preoperative cases showed that the sites of primary tumor were the stomach (5 cases, 62.5%), and small intestine (3 cases, 37.5%). One stomach lesion and one small intestine lesion showed negative findings. In follow-up cases, there were 18 PET-negative cases. Among them, two cases were considered as false negative by follow-up imaging. On the other hand, 15 cases showed positive findings at 23 lesions. Most PET-positive cases were considered as true positive except for one false-positive case, who later received surgery and was diagnosed as leiomyoma histopathologically. In 14 cases, PET findings were considered to provide additional information to conventional imaging. In eight cases among them, PET findings were considered to have influenced the decision-making of therapeutic plans. Conclusion: Our data suggest that FDG PET has an incremental value over conventional imaging for the diagnostic and therapeutic management of patients with GISTs in Japan as reported worldwide, and supports its introduction as a routine diagnostic tool for patients with GISTs.