Percutaneous radiofrequency ablation therapy for hepatocellular carcinoma: a proposed new grading system for the ablative margin and prediction of local tumor progression and its validation

Abstract

In the present study we classified the radicality of percutaneous radiofrequency thermal ablation (RFA) therapy according to the extent of the ablated margin. We measured the local recurrence rate for each radicality grade to evaluate the significance of the grading system in assessing the therapeutic effectiveness of RFA and predicting local tumor progression. This retrospective study involved 269 patients with solitary hypervascular hepatocellular carcinoma who had undergone RFA. The mean ± SD observation period after RFA, number of treatment sessions, and tumor diameter were 25.7 ± 19.9 months, 1.2 ± 0.5, and 2.1 ± 0.7 cm, respectively. Patients were evaluated using dynamic computed tomography. We classified the radicality of RFA treatment into four grades (R grades: A, B, C, and D) according to the extent of the ablated tumor margin, calculated the post-RFA cumulative local recurrence rate for each R grade, and analyzed the factors (patient characteristics, biochemical data, contiguous vessels, and tumor marker) contributing to local recurrence. The cumulative local recurrence rates at 3 years were 6.7, 17.6, 55.8, and 82.2% for Grades A, B, C, and D, respectively. Using univariate analysis, R grade, tumor size (> 2 cm), and des-γ-carboxy prothrombin (DCP) (> 200 mA U/mL) were shown to be significant factors contributing to local recurrence. However, using multivariate analysis, only the R grade was found to be a significant independent factor. The proposed R grading method is a valid and useful method for assessing treatment efficacy, and for predicting local tumor progression after RFA.