Treatment support is anticipated to improve the results of radiofrequency ablation (RFA) treatment in cases in which visualization of tumors using the conventional B-mode is unclear. In the present study, the effectiveness of treatment support for RFA reducing the local recurrence rate of hepatocellular carcinoma (HCC) that are located directly adjacent to the diaphragm, and which are difficult to visualize with B-mode ultrasound imaging, was investigated. A total of 103 HCC tumors measuring <5 cm, which were located abutting the diaphragm, and which were difficult to visualize using the B-mode, were treated using RFA. Thirty-three of those HCC tumors were treated using RFA without treatment support, whereas the remaining 70 HCC tumors were treated using RFA with treatment support, including artificial pleural effusion, contrast-enhanced ultrasonography (CEUS) with the contrasting agent, Sonazoid™, and fusion imaging, either alone or in combination to improve the visualization of the tumors. The rate of local recurrence, and factors affecting local recurrence, were analyzed. Local recurrences were confirmed in 17 of the 103 nodules (16.50%). The overall rate of local recurrence was 13.1% at 6 months, and 20.2% at 12 months. The rate of local recurrence using RFA with artificial pleural effusion was significantly lower compared with those cases of HCC tumors treated without artificial pleural effusion (P=0.008). Similarly, the rate of local recurrence for CEUS RFA with Sonazoid™ was significantly lower compared with those cases of HCC tumors treated without Sonazoid™ (P=0.00081). In a multivariate analysis, CEUS RFA with Sonazoid™ and artificial pleural effusion contributed to the decrease in the rate of local recurrence (hazard ratios, 0.075 and 0.143, respectively). Based on these results, it is possible to conclude that CEUS with Sonazoid™ as a treatment support was the most effective method for reducing the rate of local recurrences abutting the diaphragm that are difficult to visualize using B-mode ultrasonography.
Keywords: Sonazoid™; hepatocellular carcinoma; radiofrequency ablation; treatment support.