Size discrepancy between sonographic and computed tomographic/magnetic resonance imaging measurement of hepatocellular carcinoma: the necessity of tumor size measurement standardization

Objectives-There is no standardized method for size measurement of hepatocellular carcinoma. The purpose of this study was to evaluate whether the size and stage of hepatocellular carcinoma differ according to the imaging modality. Methods-This retrospective study was approved by our Institutional Review Board, and written informed consent was waived. Patients with hepatocellular carcinoma who underwent either computed tomography (CT) or magnetic resonance imaging (MRI) along with planning sonography for radiofrequency ablation on the same day were included. A total of 113 patients with 127 hepatocellular carcinomas were included. The sizes of the tumors were measured and the tumor stages were assessed on CT/MRI and sonography. The results were compared by a t test, Bland-Altman limits of agreement, and a McNemar test. Results-There was a significant difference in the hepatocellular carcinoma size between CT/MRI and sonographic measurements (mean difference, 0.26 cm; P < .0001). The sizes of 102 tumors (80.3%) were larger on sonography than on CT/MRI. Twelve tumors (9.5%) were the same size and 13 (10.2%) were smaller on sonography than on CT/MRI. There was also difference in the tumor stage (very early or not) between CT/MRI and sonography (P= .006, McNemar test). The stage was discordant in 16 of 127 tumors (12.6%). Among 69 tumors at the very early stage on CT/MRI, 14 (20.3%) were beyond the very early stage on sonography. Conclusions-The size of hepatocellular carcinoma measured on sonography tends to be larger than on CT/MRI; therefore, the tumor stage can differ between sonography and CT/MRI.