Aim: Percutaneous radiofrequency (RFA) and microwave ablation (MWA) are currently the best treatment options forpatients with liver metastases (LM) who cannot undergo a liver resection procedure. Presently, few studies have evaluated theefficacy of tumor ablation in beginner’s hands but none at all in hepatic metastasis. Our aim was to report the initial experiencewith ultrasound as a tool to guide tumor ablation in a low volume center with no experience in tumor ablation.Material and methods: We conducted a retrospective cohort study, on a series of 61 patients who had undergone percutaneous US-guided ablations for 82 LM between 2010 and 2015. Long term outcome predictors were assessed using univariate and multivariate analysis.Results: Complete ablation was achieved in 86.9% of cases (53/61). All MWA sessions (20/20) attained ablation margins >5mm, compared to 79% (49/62) for RFA sessions (p=0.031). Ablation time was significantly shorter for MWA, with a median duration of 10 minutes (range: 6-12) vs. 14 minutes (range: 10-19.5, p=0.003). There was no statistically significant difference in local tumor progression (LTP)-free survival rates between MWA and RFA (p=0.154). On univariate analysis, significant predictors for local recurrence were multiple metastases (p=0.013) and ablation margins <5 mm (p<.001), both retaining significance on multivariate analysis. Significant predictors for distant recurrence on both univariate and multivariate analysis were multiple metastases (p<0.001) and non-colorectal cancer metastases (p<0.05).Conclusion: A larger than 5 mm ablation size is critical for local tumor control. We favor the use of MWA due to its ability to achieve ablation in significantlyshorter times with less incomplete ablations.
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