Transcatheter arterial chemoembolization (TACE) is the optimal treatment option for patients with intermediate stage HCC according to the BCLC staging system. The aim of palliative treatment options is to improve the survival without greatly impairing the quality of life [8]. The goal of imaging biomarkers used in the assessment of the tumour response is to early identify the nonresponder patients in order to allow for potential changes in therapeutic plans [6].
Our study showed a significant statistical difference between mRECIST and vRECIST in the assessment of therapeutic response after intra arterial therapy of HCC whether responders or non-responders. It is also noted that many lesions were diagnosed as stable disease (nonresponders) by mRECIST are classified as partial response (responders) by vRECIST which has a great impact on therapeutic planning and further management of the patients.
Several approaches used for the assessment of tumour response to treatment include RECIST, mRECIST and more recently vRECIST. RECIST and mRECIST are widely used methods but have some limitations when applied to TACE. In their current form, RECIST and mRECIST methods analyze the residual tumour only in the axial plane which gives numerous drawbacks as they are not accurate in lesions with inhomogeneous enhancement, asymmetric regression and multiple tumours [9, 10].
TACE may result in heterogenous tumour necrosis, and as a result, the change in tumour enhancement and tumour size may become heterogeneous and this could be explained by the fact that tumours are fed by multiple arteries that are not typically treated equally. This makes some limitation to the mRECIST method of tumour response assessment [11].
A large retrospective study done by Tacher et al. [6] was done to assess the HCC response after TACE using the uni and bidimensional (RECIST, mRECIST and EASL) versus quantitative three-dimensional methods (qEASL and vRECIST). The study was performed over 290 confirmed HCC cases that underwent TACE, and in line with our findings, they found a significant statistical difference between the responders and nonresponders group when using the three-dimensional-based criteria; on the other hand, no statically significant difference was found between responders and nonresponders groups when using the bidimensional methods. They concluded that 3D methods are the criteria of choice to predict patient survival after TACE as they clearly identify the nonresponders. This agrees with our findings.
A recent study done by Moawad et al. [12] was conducted over 42 HCC cases, and the tumour response assessment was done using the manual volumetric RECIST (M-vRECIST), automated volumetric RECIST (A-vRECIST) and the mRECIST criteria. They compared the diameter changes determined through the different methods. The correlation between tumour diameter measurement changes by mRECIST and M-vRECIST revealed a statistically significant difference between both methods (P < 0.001), and this goes in line with our results. Furthermore, they compared the M-vRECIST and A-vRECIST and found strong linear correlation between the two approaches.
Welsh et al. [13] performed a study over 17 patients with HCC who underwent liver transplantation. The tumour size and volume were assessed by the RECIST and the volumetric methods, then gross pathologic measurements after hepatectomy were analyzed for tumour volumes. They found that RECIST was significantly overestimated the tumour volume by an average of 28%, while volumetric methods of tumour volume measurement was similar to gross pathologic volume.
The assessment of therapeutic response of infiltrative type of HCC is challenging due to its indistinct borders. Previous studies showed high correlation between the volumetric measurement and the pathological tumour volume. Such studies demonstrate the superiority of volumetric assessment in estimation of the real tumour volume, which is more important during assessment of treatment response [13, 14].
Lencioni et al. [15] recommends 3D volumetric analysis to be a priority in future researches. Volumetric analysis of the tumour represents the entire volume of viable portion of the tumour rather than measurement in a single axial slice, and hence, vRECIST reduced the subjectivity of 2D methods; however, such method takes a longer time for assessment which is the major drawback for volumetric analysis of the tumours.
Volumetric measurement is also able to depict tumour size changes earlier than conventional 2D methods which is crucial in patients’ follow-up. It has already been demonstrated that histopathologic tumour response correlates better with tumour volume than with axial measurements. Varzaneh et al. [16] performed a retrospective study on 173 HCC lesions that underwent TACE and liver transplantation done for 53 patients. They found that Volumetric post-TACE CT may accurately predict tumour necrosis in treated HCC lesions and well correlated with pathological findings detected after liver transplantation. They found the Mean predicted tumour necrosis in the liver transplant group was 77.6%, while at pathology was 78.7% with a statistically significant correlation between radiologically predicted tumour necrosis and pathological necrosis (r = 0.871, p < 0.001).
Another study by Chapiro et al. [17] conducted on 17 patients with HCC who underwent TACE before surgery and followed up by 3D volumetric segmentation of target lesions by MR examination before orthotopic liver transplantation or surgical resection, and they found a very good agreement between radiologically predicted liver volume and that detected pathologically after surgery.
In line with our findings, Budjan et al. [18] performed a study over 22 HCC patients who underwent TACE and assessed by both vRECIST and mECIST pre- and post-TACE by MRI, and they found lower variability and overlap errors in measuring the entire tumour volume than by measuring the enhancing components.
The study has some limitations. It was a retrospective analysis with inherited limitations to such study design. This study involved selected patients with certain criteria which did not include some common lesions such as infiltrative HCC with portal vein thrombosis. Therefore, further researches including higher number of cases and variable types of tumours that underwent different therapeutic procedures are recommended. The main limitation of the vERCIST method is that it is a time-consuming technique which needs more time for volumetric measurement and image processing.