Radiofrequency ablation versus microwave ablation for colorectal liver metastases: long-term results of a retrospective cohort surgical experience.

Background: Ablation is an alternative treatment modality for selected patients with colorectal liver metastases (CRLMs). Although initially widely performed via radiofrequency ablation (RFA), more recently, microwave ablation (MWA) is being preferred due to its perceived superiority in creating the ablation zones. The aim of this study is to compare the long-term efficacy of these two modalities performed surgically.

Methods: Patients undergoing surgical liver ablation from 2005-2023 at a tertiary center by a single surgeon for CRLM were included in a retrospective institutional review board-approved study. Outcomes were compared using Wilcoxon, Chi-square, Kaplan-Meier, and Cox multivariate regression analyses. Continuous data are presented as median (interquartile range).

Results: There were a total of 242 patients. Laparoscopic RFA was done in 121 patients with 303 lesions and laparoscopic MWA in 121 patients with 300 lesions. There was no difference between the groups regarding operative time (161 vs. 147 minutes, respectively, P=0.4), perioperative morbidity (3% vs. 8%, respectively, P=0.2) or hospital stay (1 vs. 1 day, P=0.05). Local recurrence (LR) per lesion with at least 1 year of imaging follow-up was 29% in the RFA and 13% in the MWA group (P<0.001). Based on univariate survival analysis, tumor size, blood vessel proximity, ablation margin, and ablation modality were independent predictors of LR. To control these variables, direct matching was performed. Each cohort included 189 lesions. Kaplan-Meier analysis of these cohorts showed increased LR-free survival in the MWA group vs. the RFA group (P=0.005).

Conclusions: This large study confirms our initial observation that local tumor control rate is better after MWA vs. RFA.