The Role of 18F-FDG PET/CT in the Evaluation of Gastric Cancer Recurrence

Objective: F-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has been widely used for staging, re-staging and for monitoring therapy-induced changes and response to therapy in patients with various types of cancer, but its utilization for gastric cancer has been limited. This study aimed to assess the diagnostic performance of 18F-FDG PET/CT for detecting recurrence in gastric cancer patients with radiologic or clinical suspicion of recurrence and its clinical impact on making decision. Methods: We performed a retrospective review of 130 consecutive patients who underwent PET/CT scans for post-treatment surveillance of gastric cancer between January 2008 and March 2012. The mean time between the initial diagnosis of gastric cancer and PET/CT studies was 44 weeks with a median of 18 weeks. The number and site of positive FDG uptake were analyzed and correlated with the final diagnosis by calculating the diagnostic values. We evaluated the diagnostic accuracy of PET/CT for detecting the recurrence in terms of whether or not histology had been SRC/musinous adenocarcinoma. The changes in the clinical management of patients were also evaluated according to the results of PET/CT. Results: Of all 130 patients, 91 patients were confirmed to have true recurrence. The sensitivity, specificity, positive predictive value, negative predictive value and the accuracy of PET/CT for diagnosing true recurrence on a per-person basis were 91.2%, 61.5%, 84.6%, 75.0% and 82.3% respectively. Final diagnoses were confirmed histopathologically in 59 (45.4%) of 130 patients and by clinical and radiological follow-up in the remaining 71 (54.6%) patients. In the subgroup with SRC/mucinous adenocarcinoma differentiation of the primary tumor, there was no statistically significant difference in terms of diagnostic accuracy of PET/CT on a per-person basis. In addition, PET/CT results changed the patients' management in 20 (15%) cases. Conclusions: 18F-FDG PET/CT can provide useful information in discriminating true recurrence in patients with suspected gastric cancer recurrence and may have significant impact on clinical decisions/patient management in a considerable percentage of patients.