Imaging plays an important role in the management of HCC, and the efficacy of treatment is usually monitored and assessed radiologically . Generally, targeted therapy agents induce a reduction in tumor vascularization, provocation of necrotic area, and sometimes cavitation in solid tumors, and these features have been reported in various targeted therapies of HCC .
To evaluate the changes which occurred in the tumor after locoregional interventional procedures, we use many imaging modalities such as US, CECT, and dynamic MRI. However, lipidol deposits in TACE can make the evaluation more difficult in CECT, and dynamic MRI are the most commonly used tools to evaluate patients .
In HCC patients managed with TACE, contrast-enhanced triphasic CT scan gives information about the tumoral size and its vascularity which may affect the recurrence or viability of the tumor. However, the main limitation of CT was the presence of hyperdense lipidol which may mask the viable intra-lesional tumor tissue .
FDG-PET depends on the assessment the metabolism of the tumor managed by TACE which is important in oncology. It has the advantage of examining the whole body as well, so we can assess the intra- and extra-hepatic disease in single examination which is crucial for patients who planned for hepatic transplantation [14, 15].
Many studies had been done on the evaluation of the role of PET scan in evaluation of loco-regional ablation of the HCC. In this study, the efficiency of FDG-PET scan was compared to that of the CECT in the evaluation the local tumor residue/recurrence of HCC after TACE.
It was found that the CECT had a sensitivity of 82%, specificity of 66.7%, positive predictive value (PPV) of 87.5%, negative predictive value (NPV) of 57.1%, and accuracy of 78.2%. However, PET had sensitivity and specificity of 100% and 66.7%, respectively. Positive predictive value (PPV) was 89.5%, negative predictive value (NPV) was 100%, and accuracy was 91.3%.
Compared to Jinpeng et al. study  which studied the recurrence of HCC after (TACE) in 29 patients, they found the sensitivity of PET was 95.4% while the sensitivity of CECT was 63.8%.
Also, Song et al.  study done in 2015 showed that F-FDG-PET/CT was found to be superior to CECT for the detection of viable tumor in patients with HCC after TACE.
Azab et al.  study concluded that FDG-PET/CT showed higher sensitivity and specificity than contrast CT in the evaluation of HCC after local therapy of HCC (which includes radiofrequency and TACE) whatever the degree of tumor vascularity.
Also, Wenhui et al.  study proved that 18F-FDG PET/CT has diagnostic value in detecting viable HCC patients after TACE. Therefore, 18F-FDG PET/CT may provide valuable information that can be used in the treatment response evaluation and clinical decision-making process.
All the above-mentioned studies’ results match with my results which showed that FDG PET was more accurate in the diagnosis of residual or recurrence HCC post-TACE than CECT which has an important role in deciding if the patient will take another session of TACE or not. But it still of limited role regarding cost, radiation exposure, more time of examination, and availability.
Also, using FDG-PET accuracy depends on the grade of biological activity of the tumor, meaning that the low biologically active tumor (low grade) may not be evaluated well by FDG-PET study.
The relatively small number of patients included in this study was considered as one of the weak points. Also, this study depends on the follow-up (imaging and laboratory) as the reference standard; however, histopathological correlation of the residue/recurrence is still more reliable as a reference standard.