Role of 18-F FDG-PET/CT in the Detection of Local Tumor Residue/Recurrence in Hepatocellular Carcinoma (HCC) Post Hepatic Therapeutic Intervention

Background: Hepatocellular Carcinoma (HCC) is the cause of 250,000 deaths worldwide each year. Early HCC is typically clinically silent, and the disease is often well advanced at the first manifestation. Several minimally invasive percutaneous techniques are now available to help manage localized HCC. The most used loco-regional therapy consists of imaging-guided percutaneous ethanol or thermal ablation, such as Radiofrequency Ablation (RFA) and microwave ablation, TACE, and trans-arterial radioembolization. Differentiation between post ablation/embolzied tissue changes and residual disease is difficult with morphologic imaging modalities such as ultrasonography, Computed Tom-ography (CT), and Magnetic Resonance (MR) imaging, thus limiting the use of these modalities to detection of residual disease early after RFA. Lesions that show increased FDG uptake at PET become completely photopenic immediately after ablation/emboliza-tion, a finding that is suggestive of the completeness of ablation. Focal areas of increased FDG uptake within the ablated zone are suggestive of residual disease. Reactive tissue changes such as inflammation are depicted in the periphery of the ablated lesion and show a uniform low-grade FDG uptake, which can be differentiated from the focal, nodular intense uptake in areas of residual disease. Objective: The purpose of this study is to explore the effectiveness of combined PET/CT examination detection of local tumor residue/recurrence in Heptocellular Carcinoma (HCC) post hepatic therapeutic intervention. Patients and Methods: This is a retrospective study carried out in Alfa Scan Radiology Center from March 2013 to March 2015 for in patients pathologically proven to have HCC on top of liver cirrhosis after session or more of local therapy. A total number of 40 patients: 33 (82.50%) males and 7 (17.50%) females with a median age 57.55±6.93 (range, 42- 75). The reference standard to determine the accuracy of the imaging findings is follow-up of the patient by PET/CT and other modalities, clinical data and laboratory findings. Results: CECT had sensitivity and specificity of 76.7%, 100% respectively with Positive Predictive Value (PPV) of 100%, Negative Predictive Value (NPV) of 58.8% and accuracy of 82.5%. PET had sensitivity and specificity of 96.7%, 100% respectively with Positive Predictive Value (PPV) of 100%, Negative Predictive Value (NPV) of 90.9% and accuracy of 97.5%. Conclusion: FDG-PET/CT proved to be highly sensitive and specific in the assessment of hepatic bed after local therapy of HCC regardless the degree of tumor vascularity that could limit detecting residual disease based on contrast cT/MRI imaiging