Safety limit of large-volume hepatic radiofrequency ablation in a rat model

Abstract

Background: Large-volume hepatic radiofrequency ablation (RFA) has been used to treat large liver tumors, but its safety limit is unknown. This study aimed to investigate the possible systemic responses of large-volume hepatic RFA and to estimate its safety limit in normal and cirrhotic rats. Hypothesis: Large-volume hepatic RFA causes a significant systemic inflammatory reaction. Design: Experimental study. Setting: University teaching hospital. Intervention: Using the Cool-tip RF System (Radionics, Burlington, Mass), RFA was performed for different percentages of the liver volume by weight in normal and cirrhotic Sprague-Dawley rats. Main Outcome Measures: Changes in concentrations of serum inflammatory markers (tumor necrosis factor α [TNF-α] and interleukin [IL] 6), functions of various end organs, and survival rates were assessed. Results: In the normal liver groups, the concentrations of TNF-α and IL-6 were significantly elevated in the early postoperative period when 50% (mean ± SD TNF-α concentration, 130.3 ± 15.6 pg/mL; mean ± SD IL-6 concentration, 163.2 ± 12.2 pg/mL) and 60% (mean ± SD TNF-α concentration, 145.7 ± 13.0 pg/mL; mean ± SD IL-6 concentration, 180.8 ± 11.0 pg/mL) of the liver volume were ablated compared with the control group (mean ± SD TNF-α concentration, 30.4 ± 9.9 pg/mL, P < .001; mean ± SD IL-6 concentration, 28.4 ± 6.7 pg/mL, P < .001). The concentrations of TNF-α and IL-6 in other groups remained similar to those in the control group. Thrombocytopenia, prolonged clotting time, and interstitial pneumonitis occurred when 50% and 60% of the liver volume were ablated. The 4-week survival rates were 100%, 60%, and 0% when 40%, 50%, and 60%, respectively, of the liver volume were ablated. Similar systemic inflammatory responses and poor survival rates were observed among the cirrhotic liver groups when 30% and 40% of the liver volume were ablated. Conclusions: The normal rats can tolerate RFA of 40% of the liver volume with minimal morbidity and no mortality whereas the cirrhotic rats can only tolerate 20% of the ablated liver volume. Beyond that limit, RFA would cause significant systemic inflammatory responses and poor survival. ©2006 American Medical Association. All rights reserved.