An Emory University researcher has established the diagnostic power of a simple contrast-enhanced MRI protocol that informs surgeons about the presence and extent of hepatocellular cancer in cirrhotic livers that are scheduled for transplantation.
"HCC is very common in patients with liver cirrhosis," said Dr. Thomas C. Lauenstein, an assistant professor of radiology at Emory University. "Accurate detection is especially important in these cases because of their effect on treatment options, especially when we talk about transplantation."
Gadolinium-enhanced MRI has been found to be most accurate compared to other MR, CT, and ultrasound protocols despite inconsistent findings in the medical literature. Previous studies of gadolinium-enhanced MRI of hepatocellular cancer have generated inconsistent results, with sensitivities to disease ranging from 68% to 92%.
This prospective study examined the accuracy of the approach before liver transplantation for 115 patients with liver cirrhosis. All scans of diseased livers were performed on a 1.5T scanner within 90 days before transplantation.
While following a comprehensive protocol, Lauenstein focused on the dynamic T1-weighted images. A study published in Radiology last year by Dr. Elizabeth Hecht showed that contrast-enhanced T1-weighted MR imaging can be used as a stand alone technique for finding focal lesions. T2-weighted imaging does not provide additional information, Lauenstein said.
Three criteria were used for a positive diagnosis of HCC: increased arterial enhancement, delayed washout on the late venous phase, and ring enhancement around the lesion. A lesion was deemed positive for HCC when at least two those three features were present.
A subanalysis grouping lesions smaller and larger than 2 cm was performed. Histopathology was the standard of reference.
Histopathology showed HCC in 27 of the 115 transplant patients. Sensitivity and specificity of dynamic T1-weighted MR were 88.9% and 97.7%, respectively. The approach correctly evaluated 24 of the 27 patients with HCC lesions. MRI was responsible for two false positives and one false negative compared to histopathology. Followup analysis indicated, however, that MRI had indeed correctly characterized two lesions as HCC that had been inaccurately assessed by histopathology as dysplastic nodules.
Thirty-six HCC lesions were identified through histopathology. Half were smaller than 2 cm and half were larger. MRI identified 28 of those tumors: all 18 that were greater than 2 cm and 10 that were smaller.
It also flagged two false positive and six false negatives. On that basis, Lauenstein calculated an overall lesion-based sensitivity of 77.8%.
"There were also two lesions that we called dysplastic nodules because they only showed increased arterial enhancement," Lauenstein said. They were actually HCC tumors.
MRI's sensitivity for lesions 2 cm or smaller rose slightly, from 55.6% to 66.7%, when the two dysplastic nodules were taken into account.
Gadolinium-enhanced MRI is very sensitive and specific for the depiction of HCC when the lesions are larger than 2 cm. For smaller lesions it is only moderately accurate. From a clinical perspective, no patient underwent needle-guided biopsy before transplantation.
