Monitoring Hepatocellular Carcinoma Using CT and MRI

Monitoring Hepatocellular Carcinoma Using CT and MRI

Chemoembolization for treatment of hepatocellular carcinoma improves survival, converts nonsurgical lesions to surgical lesions, and acts as a bridge to transplant.

Abdominal imaging, such as contrast-enhanced CT or MRI, is the most feasible mode of monitoring for tumor viability, but the effectiveness is not well known.

To accurately check for sensitivity and specificity, comparison of radiologic findings with histology is necessary.

A recent study which compared contrast-enhanced CT and MRI indicated that both have low accuracy rates to follow-up chemoembolization for hepatocellular carcinoma, but argues that in this instance, MRI for abdominal imaging is better.

The Study
These researchers did a retrospective review of patients who had orthotopic transplants after chemoembolization in their institution.

Methodology
Of these 55 patients, 31 had radiologic studies prior to transplantation after chemoembolization. Of 31 studies, 20 had a CT, 10 had an MRI, and 1 had both.

Results
13 patients (41%) had what was considered viable tumor on imaging; however, 22 (70%) had viable tumor on histopathologic evaluation. This leads to an overall sensitivity of 35%, and an overall specificity of 64%.

When comparing modalities, the accuracy rate for CT was 43%, with a 36% sensitivity and a 57% specificity. With CT, false negatives were 42% microscopic disease and 33% macroscopic.

For MRI, the accuracy rate was 55%, with a 43% sensitivity and a 75% specificity, with the majority of false negatives being microscopic disease (60%).

Reviewer’s Comments
Histology and pathologic evaluation of the liver is the gold standard of determining presence or absence of disease. It is not practical or feasible to use this method in every patient after chemoembolization, therefore we must rely on abdominal imaging to do so for us.

The authors feel that the relatively low sensitivity and specificity of CT in this study are due to the small tumors found in this study.

Newer CT imaging, including automated whole-liver evaluation of changing attenuation values on quadruple phase hopefully will improve the accuracy of CT imaging of the abdomen post-chemoembolization.

MRI has become more popular as the modality of choice for follow-up, and this study justifies that, but there are drawbacks that make interpretation difficult.

There is a dynamic early phase enhancement followed by decline in late phase during imaging that may indicate viable tumor but may not differentiate it from things like inflammation.

The LAVA imaging in this study, a newer 3-dimensional dynamic spoiled gradient echo T1-weighted sequence with fat suppression, yielded an accuracy of 55%.

Limitations of this study include its small sample size; there is not enough power to determine the statistical significance between MRI and CT.

Presence of microscopic foci is below the current threshold of detection. Despite the reportedly low accuracy and sensitivity of this study, this study supports use of MRI rather than CT for follow-up after chemoembolization. It claims that contrast-enhanced CT and MRI both have low accuracy rates to follow-up chemoembolization for hepatocellular carcinoma, but MRI is better. We look forward to seeing larger sampling to support this theory.

Author: Sharon Gonzales, MD
Reference:
Hunt SJ, Yu W, et al. Radiologic Monitoring of Hepatocellular Carcinoma Tumor Viability After Transhepatic Arterial Chemoembolization: Estimating the Accuracy of Contrast-Enhanced Cross-Sectional Imaging With Histopathologic Correlation. J Vasc Interv Radiol; 2009;20 (January): 30-38