Diagnostic value of F-18 FDG PET/CT for local and distant disease relapse surveillance in surgically treated RCC patients: Can it aid in establishing consensus follow up strategy?

BACKGROUND: Aim of the study was to evaluate the diagnostic performance of FDG PET-CT for the detection of local and distant disease relapse in surgically treated patients with renal cell carcinoma (RCC). MATERIAL AND METHODS: This retrospective study includes 96 patients underwent FDG PET-CT scanning in the post-surgical follow up within the first 6-12 months referred to nuclear medicine department, to perform PET/CT study. Each patient underwent FDG PET-CT with low dose CT, followed immediately by full dose Ce-CT. Sites of the relapse were categorized into local and distant recurrence. Distant recurrence sites were divided into lymph nodes, lung, bone, and other soft tissue sites. The final diagnosis of disease status was made on subsequent follow up by conventional imaging (CT/MRI), FDG PET-CT, or histopathology whenever possible. RESULTS: Local and/or distant disease relapse was confirmed in 69 (71.9%) patients and the rest 28.1% were free. Regarding local recurrence FDG PET-CT showed specificity of 100% compared to 98.6% with Ce-CT (p > 0.05) and higher sensitivity noted with Ce-CT (100%) compared to 96% with FDG PET-CT. For global distant sites of metastases Ce-CT revealed high sensitivity and NPV of 93.3% & 96.9% respectively yet lower specificity (93.96%) and PPV (87.5%) was seen with Ce-CT compared to 99.6% and 99.1% with FDG PET-CT respectively. The higher Ce-CT sensitivity was attributed to its ability to detected 100% of cases of lung metastases compared to 80.6% with FDG PET-CT (P-value < 0.05). CONCLUSION: FDG PET-CT appears to be a very efficient tool in post-surgical surveillance of patients with RCC with notable ability to probe even uncommon sites of distant recurrence.