Percutaneous radiofrequency ablation therapy for patients with hepatocellular carcinoma during occlusion of hepatic blood flow: comparison with standard percutaneous radiofrequency ablation therapy.

Abstract

I read with great interest the article by Yamasaki et al. regarding balloon-occluded radiofrequency (RF) ablation of hepatocellular carcinoma.1 The issue of limitation due to the heat sink effect during thermal ablation has been explored in depth by many experimental studies using animal models.2-4 In terms of in vivo investigation, Dr. Yamasaki's trial warrants significant interest from physicians who perform thermal ablation. Despite having conducted a retrospective study, Yamasaki et al. demonstrated the importance of the heat sink effect in the in vivo study by showing that interruption of hepatic arterial flow during RF ablation led to an increase in the volume of ablated tumor. Although I agree with most of the points addressed by Yamasaki et al., I feel it is necessary to express two points of concern about the interpretation and future application of the study results. First, discussion of the heat sink effect issue recently has changed its focus from how to ablate a large volume to how to ablate the desired area (tumor plus safety margin), which includes the perivascular area, where the greatest heat sink effect has been observed as the effectiveness of ablation devices has improved. In addition, the effect of intranodular vascularity on RF ablation (RFA) has been emphasized in previous investigations. Therefore, the following information would have given the results of the study more clinical impact: 1) data regarding the proximity of each nodule to the adjacent vessels; 2) data regarding any differences between balloon-occluded and standard RFA in terms of the ablated effect on perivascular area; 3) data regarding any differences between treatment groups in terms of the hypervascularity (as measured with computed tomography scans) of each tumor; and 4) data regarding any differences between treatment groups in terms of local recurrence rate and/or survival rate. Second, we may be able to maximize therapeutic effects by combining RF therapy with preexisting treatment modalities such as transcatheter arterial embolization, percutaneous ethanol injection, and systemic chemotherapy. Nonetheless, we should carefully weigh the pros and cons of each type of combined therapy, with consideration of the real clinical benefit, the complexity and invasiveness of the combined treatment, potential complications and comorbidity, and cost effectiveness. In my opinion, it is not necessary to consider using balloon-occluded RFA to treat tumors 3–4 cm in size (provided that they are not abutting major vessels), because we can ablate tumors of such size and their safety margins (> 5 mm) using currently available RF equipment. Although balloon-occluded RFA may increase the amount of ablated lesion, the desired volume can be ablated simply by using one or two additional cycles of standard ablation. Doing so can eliminate the need for additional invasive angiographic procedures. In conclusion, we should await the evidence regarding clinical benefit in terms of local control rate and survival before declaring combined RFA with balloon occlusion to be a better treatment option than standard RFA. Therefore, I currently recommend balloon-occluded RFA only for patients with lesions that are greater than 5 cm in diameter or abut major intrahepatic vessels.