CT-guided Radiofrequency Ablation for Hepatocellular Carcinomas That Were Undetectable at US: Therapeutic Effectiveness and Safety

Purpose: To determine the therapeutic effectiveness and safety of computed tomography (CT)-guided radiofrequency (RF) ablation for hepatocelluar carcinomas (HCCs) that were undetectable at ultrasonography (US). Materials and Methods: CT-guided RF ablation with use of internally cooled electrodes was performed in 66 patients with 97 HCCs (diameter range, 3-39 mm) in 78 sessions. Two radiologists retrospectively evaluated in consensus the presence or absence of local tumor progression as well as the complications at CT performed immediately after RF ablation and at 1-, 3-, 6-, and 12-month follow-up. The relationship between the occurrence of pneumothorax and the electrode length in the lung in patients treated with the transpulmonary approach was statistically evaluated with use of the Mann-Whitney test. Results: The technical success rate of CT-guided RF ablation immediately after RF ablation was 97% (94 of 97 HCCs). The primary technique effectiveness rates of complete ablation 1, 3, 6, and 12 months after RF ablation were 97% (94 of 97 HCCs), 94% (91 of 97 HCCs), 84% (81 of 96 HCCs), and 74% (66 of 89 HCCs), respectively. Major complications were observed in six of the 78 treatment sessions (7.7%). In five of these six sessions, pneumothorax developed immediately after RF ablation; the remaining complication was tumor seeding along the electrode tract. Self-limiting pneumothorax was observed in 12 of 38 sessions (32%) in which the transpulmonary approach was used. The electrode length in the lung was not statistically related to the occurrence of pneumothorax (P = .26). Conclusions: For HCCs that are undetectable at US, CT-guided RF ablation is effective and relatively safe.