Can FDG PET/CECT accurately restage patients of stomach carcinoma?

Objectives: To evaluate the diagnostic performance of contract enhanced F-18 FDG PET/CT in restaging of stomach carcinoma patients.

Methods: We retrospectively analyzed the records of 60 patients with carcinoma stomach (49 male, 11 female) aged 22-84 years. All these patients were treated either with surgery, radiotherapy or chemotherapy alone or in combination and were referred for F-18 FDG PET/CT on the basis of clinical/radiological suspicion of residual or recurrent disease or for post-therapy monitoring. Two experienced nuclear medicine physicians analyzed all studies independently and any abnormal tracer uptake with corresponding lesion on CECT was interpreted as positive for recurrence. Histopathological examination and clinical or imaging follow up were taken as gold standard.

Results: Of the total 60 patients, F-18 FDG PET/CT detected FDG avid lesions in 41 patients, which were considered positive for malignancy. Out of these 41, local recurrence with or without regional lymph nodes was detected in 27 (65.8%) patients and only metastatic lesions were detected in 9 (15%) patients. Out of 27 patients with local recurrence, 4 had regional lymph nodes and 7 patients had distant metastases. Out of 7 patients with distant metastases, distant/regional lymph nodes, lung, liver, skeleton, mesenteric and peritoneal metastases were noted in 5, 3, 4, 2, 2 and 1 patient respectively. Additionally, in 2 patients, lesions in other organs were detected which were confirmed on histopathology as primary metachronous lung and prostate cancers. Sensitivity, specificity, PPV, NPV and accuracy of F-18 FDG PET/CT were 83.72 %, 70.59 %, 87.80 %, 63.16 % and 80% respectively for residual/recurrence disease detection. On ROC curve analysis, SUVmax >2.6 had sensitivity and specificity of 62.8% and 82.4% respectively for detection of recurrent/metastatic disease on F-18 FDG PET/CT (Area under the ROC curve is 0.729 at 95% Confidence Interval (P value 0.0004).

Conclusion: F-18 FDG PET/CT has high diagnostic accuracy for detection of residual/recurrent disease in stomach cancer after treatment. Metachronous primary malignancy may also be incidentally detected. Research Support: N A