Hepatocellular Carcinoma: Stiffness Value and Ratio to Discriminate Malignant from Benign Focal Liver Lesions

Purpose: To investigate the use of stiffness value and stiffness ratio (ratio of lesion to background liver parenchyma values) to discriminate malignant from benign focal liver lesions by using histologic results as the reference standard. Materials and Methods: This study was approved by the institutional review board, and written informed consent was obtained. Three hundred seventy-three patients with focal liver lesions proven at histologic examination underwent measurement of liver stiffness with elastography point quantification. First, stiffness values in two regions of the background liver parenchyma (at 0.5-2 cm and >2 cm from the lesion periphery) near 163 hepatocellular carcinomas were analyzed to determine a reference background liver for calculating the stiffness ratio. Second, the use of the lesion stiffness value and the stiffness ratio for prediction of liver malignancy was investigated in a cohort of patients with 58 benign and 201 malignant lesions. Results were validated in another independent cohort of patients with 25 benign and 89 malignant lesions by using analysis of the area under the receiver operating characteristic (AUC) curve. Results: The coefficient of variation for the background liver at 0.5-2 cm from the lesion was higher (196%) than that at greater than 2 cm from the lesion (66%). In the development phase, diagnostic accuracy with use of the stiffness value was significantly higher than that with use of the stiffness ratio for discrimination of malignant from benign lesions (AUC, 0.86 vs 0.66, respectively; P < .001). Diagnostic performance with the stiffness value was lower than that with the stiffness ratio (AUC, 0.53 vs 0.86, respectively; P < .001) for discrimination of cirrhotic nodules from other benign lesions. Diagnostic performance with the stiffness value was significantly lower than that with the stiffness ratio (AUC, 0.58 vs 0.71 respectively; P = .007) for discrimination of metastasis from primary liver cancers. In the validation phase, similar findings were revealed for the discrimination of malignant from benign lesions (AUC, 0.87 vs 0.67; P < .001) and discrimination between metastasis and primary liver cancers (AUC, 0.49 vs 0.73; P < .001). Conclusion: Use of stiffness values measured in the liver parenchyma at more than 2 cm from the lesion allowed better diagnostic performance than did values measured in a region closer to the tumor. Stiffness value was more accurate than stiffness ratio for differentiation of malignant from benign focal liver lesions, but the stiffness ratio might be useful for subclassification of benign and malignant lesions. (C) RSNA, 2015