Ji Young Lee MD, Presenter: Nothing to Disclose

Young-Sun Kim MD, Abstract Co-Author: Nothing to Disclose

Won Jae Lee MD, Abstract Co-Author: Nothing to Disclose

Hyunchul Rhim MD, PhD, Abstract Co-Author: Nothing to Disclose

Hyo Keun Lim MD, Abstract Co-Author: Nothing to Disclose

Dongil Choi MD, Abstract Co-Author: Nothing to Disclose

To elucidate minimal ablative margin of radiofrequency ablation (RFA) of HCC over 2cm required for preventing local tumor progression (LTP) and the effect of hepatic vessels on ablative margin using image fusion and multi-planar reformatting (MPR) of pre- and post-RFA CT

From Dec 2003 to Nov 2007, we percutaneously ablated 236 previously-untreated HCCs over 2cm in 215 patients (M:F=165:50, mean age 59.1) who were followed-up for more than 1 year. Retrospectively, we evaluated technique effectiveness rate at 1 month and cumulative LTP rate in this group. For quantitative analysis of ablative margins, 103 patients (M:F=77:26, mean age 59.7) with 110 HCCs were chosen after excluding patients without appropriate CT. Using CT workstation (Virtual place, Aze), we fused CTs before and after RFA and performed radial MRP of fused images with its axis of rotation at the center of tumor. We sought for the thinnest ablative margin, effect of hepatic vessels on ablation zone, and concordance between LTP and point of the thinnest margin. Considering only concordant LTPs, incidence of LTP were calculated at each thickness of margin by millimeter.

Patients were followed-up for 12.0~48.1 months (median 26.8). Technique effectiveness rate was 99.2%. Cumulative LTP rates at 1, 2, and 3 year were 12.7%, 22.3%, and 28.1%, respectively. In 110 tumors chosen, the thinnest ablative margins ranged 0-6mm (1.0±1.4) and it was 0mm in 51.8% (57/110). In 47.3% (52/110), heat sink-induced indentation of ablation zone, mostly by hepatic artery / portal vein (49/52), contributed to the thinnest ablative margin. LTP was noticed in 27.3% (30/110). And, 83.3% of them (25/30) showed concordance between LTP and the thinnest ablative margin. Incidences of concordant LTP were 22.7% (25/110), 18.9% (10/53), 5.9% (2/34), and 0% (0/15) in tumors with the thinnest ablative margin ≥0mm, ≥1mm, ≥2mm, and ≥3mm, respectively.  

Three dimensional quantitative analysis of ablative margin of RFA of HCC revealed that vessel-induced indentation of the ablation zone is a major cause of insufficient ablative margin and the establishment of ablative margin ≥3 mm surrounding the tumor is necessary to prevent LTP.

To prevent local tumor progression, percutaneous RFA of HCC should be performed more aggressively when the tumor is located within 3mm from the adjacent hepatic artery / portal vein branch.

Lee, J, Kim, Y, Lee, W, Rhim, H, Lim, H, Choi, D, Relationships between Ablative Margin and Local Tumor Progression after Percutaneous Radiofrequency Ablation of Hepatocellular Carcinoma: Three-dimensional Quantitative Analysis Using CT Image Fusion and Multi-planar Reformatting.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6016629.html