San Francisco—Morris Sherman, MD, PhD, associate professor of medicine at the University of Toronto, spoke about diagnostic imaging for hepatocellular carcinoma (HCC) at the 2011 American Society of Clinical Oncology Gastrointestinal Cancers Symposium.

“Instead of requiring two more or less consecutive contrast radiographic studies to define if a lesion is positive for cancer or not, one image is now considered acceptable if the findings are typical,” he said, referring to the new American Association for the Study of Liver Disease (AASLD) guidelines on HCC. “If one study’s findings are not typical but the second study’s are, that is also good enough. This cuts down on the total number of radiographic studies required, and also reduces the number of biopsies that are needed.”

The rationale for the updated AASLD guidelines largely pertains to small lesions. More than half of nodules less than 1 cm are not HCC. Biopsy of small lesions is difficult and unreliable, and the appearance of small HCC lesions is rarely typical. “Putting a needle accurately into a very small lesion is a big problem,” Dr. Sherman said. “The false-positive rate is very high, hence the recommendation is to watch these lesions.”

New Diagnostic Algorithm

In the new diagnostic algorithm put forth in the AASLD guidelines, a nodule identified by ultrasound is stratified based on size and treated accordingly. For lesions less than 1 cm, the AASLD recommends a repeat ultrasound in three months followed by surveillance. If the lesion grows or changes in character, further investigation is warranted. For lesions greater than 1 cm, additional work-up is necessary, including a four-phase multidetector computed tomographic (CT) scan or dynamic contrast-enhanced magnetic resonance imaging (MRI) test. Lesions with arterial hypervascularity and venous and delayed-phase washout are considered positive for HCC. If negative for these features (i.e., the appearance is atypical), the other contrast-enhanced study (i.e., MRI or CT) should be performed. If those results also are negative, the lesion should be biopsied, the guidelines state.

This strategy minimizes resource utilization. If the first scan does not show typical features of HCC, then a second contrast-enhanced study is performed. This increases the sensitivity, with little loss of specificity, and reduces the frequency of biopsies, Dr. Sherman explained.

However, “if the objective is to maximize accuracy and never treat incorrectly, then two contrast-enhanced studies should be done, as per the older guidelines.” But this strategy results in a significant number of biopsies, Dr. Sherman noted.

Important Caveats

“These changes are reflected in the new guidelines, but there are several important principles to keep in mind,” Dr. Sherman said.

First, the radiographic features of HCC, when present, are highly specific. The lesion is more enhanced than the surrounding liver in the arterial phase and less enhanced than the surrounding liver in the venous phase of the examination. When these features are not present, a biopsy is required, he said. Second, the new guidelines apply only to situations when HCC is likely to be identified, as in patients known to be at risk. In patients with a liver mass and no underlying liver disease, the algorithm does not apply and the approach is different. If the lesion is likely to be malignant or otherwise requires resection, biopsy is not indicated because the diagnosis will be confirmed from the surgical specimen.

Hashem B. El-Serag, MD, MPH, chief of gastroenterology and hepatology at Baylor College of Medicine, in Houston, said, “the new guidelines bring an enlightened interpretation of the existing literature on HCC diagnosis. However, the evidence base from which these guidelines stem is mostly retrospective data and nonrandomized clinical trials. Furthermore, the utility of the diagnostic guideline has not been tested. Local resources and expertise should be considered when applying the guidelines, in particular, the ability to exclude HCC based on cross-sectional imaging studies.”

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Also See: AASLD Publishes New Guideline on HCC