Correlation of tumor response on CT with pathologically proven necrosis in hepatocellular carcinoma treated by conventional transcatheter arterial chemoembolization: threshold value of intratumoral Lipiodol accumulation predicting tumor necrosis.

PURPOSE: To evaluate associations between pathology and CT assessments made according to the mRECIST in HCC treated by conventional TACE (cTACE), and to identify predictors of complete tumor necrosis.
METHODS: From March 2016 to July 2018, 83 patients with a total of 100 masses were retrospectively included. Patients underwent sequential cTACE and portal vein embolization, and later hepatic surgery. Evaluation of treatment response and measurement of baseline lipiodol accumulation as mean HU was performed on CT at the time point closest to the time of operation (mean, 54.5 days after cTACE). Significant predictors associated with complete necrosis were identified by multivariate analysis. The optimal cut-off HU value of lipiodol accumulation for prediction of complete necrosis was determined using a ROC analysis.
RESULTS: According to mRECIST, complete response (CR, n = 70) and partial response (n = 30) were classified. 34.3% (24/70) masses classified as CR according to mRECIST were found to have viable lesions on pathology. On multivariate analysis, mean HU of lipiodol accumulation was the only significant predictor of complete necrosis (p = .003, odds ratio 1.746, 95% CI 1.201-2.539). On ROC analysis, 460 HU as a cut-off value was significantly associated with complete necrosis (67.4% sensitivity, 75.0% specificity).
CONCLUSIONS: A threshold value for lipiodol accumulation > 460 HU was highly sensitive and specific for complete necrosis, even in complete response according to mRECIST. Therefore, if lipiodol accumulation is insufficient in post-TACE CT, recurrence should be monitored more sensitively.