Radiofrequency Ablation of Hepatocellular Carcinoma: Correlation Between Local Tumor Progression After Ablation and Ablative Margin

Abstract

OBJECTIVE: To identify the determinants of tumor progression, we examined the ablation zones and patterns of local progression of small single primary hepatocellular carcinomas after radiofrequency ablation. MATERIALS AND METHODS: Eighty-five patients with single primary hepatocellular carcinoma less than 3 cm in diameter underwent complete tumor ablation. Clinical and biochemical features, tumor characteristics, tumor location within 5 mm from intrahepatic vessels, needle biopsy before treatment, and presence of ablative margin of 5 mm or more were statistically analyzed as determinants of local tumor progression. The Kaplan-Meier method and a Cox model were used for the analyses. Patterns of local tumor progression were examined by image analysis. RESULTS: During a median observation period of 30.3 months, 14 (16.5%) of the 85 patients had local tumor progression. The results of the log-rank test showed that the presence of vessels contiguous with the tumor (p = 0.0292) and the absence of an ablative margin of at least 5 mm (p = 0.019) significantly correlated with local tumor progression. Cox regression analysis showed that the absence of an ablative margin of at least 5 mm was an independent factor (p = 0.04). The most common pattern of local tumor progression was a single viable outgrowth from the side of the ablated area when the ablative margin was less than 5 mm. Multiple viable outgrowths were observed in one case despite the presence of an ablative margin greater than 5 mm. CONCLUSION: An ablation zone with an ablative margin of 5 mm or greater was the most important factor for local control of hepatocellular carcinoma.