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.

Objective:Our aim was to assess the diagnostic performance of integrated positron emission tomography/computed tomography (PET/CT) in the follow-up of breast cancer patients, who underwent a PET/CT scan due to a suspicion of recurrence based on elevated levels of serum tumor markers.Methods:Seventy-seven consecutive patients were included in this study. PET/CT scan results were compared with the final diagnoses that were obtained from histopathological sampling or a minimum 6 months of radiological follow-up. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and the diagnostic accuracy of PET/CT for detecting recurrence were calculated.Results:All 77 patients had increased serum cancer antigen 15-3 levels while 37 had increased serum carcinoembryonic antigen levels. According to PET/CT scan results, 59 of 77 patients (PET/CT positive) had local recurrence and/or distant metastasis while there was no pathological finding in 18 patients (PET/CT negative). In a follow-up of minimum 6 months, tumor recurrence was confirmed in 58 of “PET/CT positive” patients while no tumor recurrence was detected in 16 of “PET/CT negative” patients. According to these results the sensitivity, specificity, PPV, NPV and the diagnostic accuracy of PET/CT for detecting recurrence on a per-person basis were calculated as 98%, 88%, 96%, 94% and 96%, respectively.Conclusion:In case of elevated levels of serum tumor markers, PET/CT has a high diagnostic accuracy in detecting tumor recurrence in patients with breast cancer, and it is an effective modality that can be used in addition to conventional imaging techniques.

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We present the case of a 56-year-old man with the clinical diagnosis of ocular melanoma. As a part of staging, he underwent an F-18 FDG PET/CT scan for investigating distant metastasis. On PET scan, an increased focal area of F-18 FDG uptake was seen behind patient's right knee that can be confused with distant metastasis. On CT scan, there was a fluid density in the same location. The probable diagnosis was Baker’s cyst. Later, USG and MRI confirmed this diagnosis. Conflict of interest:None declared.