Microwave (MWA) and radiofrequency ablation (RFA) are main ablative techniques for hepatocellular carcinoma (HCC) and colorectal liver metastasis (MT). This randomized phase 2 clinical trial compares the effectiveness of MWA and RFA as well as morphology of corresponding ablation zones. HCC and MT patients with 1.5–4 cm tumors, suitable for ablation, were randomized into MWA or RFA Groups. The primary endpoint was short-to-long diameter ratio of ablation zone (SLR). Primary technical success (TS) and a cumulative local tumor progression (LTP) after a median 2-year follow-up were compared. Between June 2015 and April 2020, 82 patients were randomly assigned (41 patients per group). For the per-protocol analysis, five patients were excluded. MWA created larger ablation zones than RFA (p = 0.036) although without differences in SLR (0.5 for both groups, p = 0.229). The TS was achieved in 98% (46/47) and 90% (45/50) (p = 0.108), and LTP was observed in 21% (10/47) vs. 12% (6/50) (OR 1.9 [95% CI 0.66–5.3], p = 0.238) of tumors in MWA vs. RFA Group, respectively. Major complications were found in 5 cases (11%) vs. 2 cases (4%), without statistical significance. MWA and RFA show similar SLR, effectiveness and safety in liver tumors between 1.5 and 4 cm.

Purpose: Microwave (MWA) and radiofrequency ablation (RFA) are main ablative techniques for hepatocellular carcinoma (HCC) and colorectal liver metastasis (MT). This randomized phase 2 clinical trial compares the effectiveness of MWA and RFA in medium-sized liver tumors.Methods: HCC and MT patients with 1.5 to 4 cm tumors suitable for ablation were randomized into MWA or RFA Groups. The primary endpoints were primary technical success (TS) and local tumor progression (LTP) rate after a 2-year follow-up. Secondary endpoints were safety and overall survival. Results: Between June 2015 and April 2020, 82 patients were randomly assigned (41 patients per group). For the per-protocol analysis, three patients were excluded. Median follow-up was 27 months (MWA group) and 23 months (RFA Group). The TS was achieved in 98% (46/47) and 90 % (45/50) (p=0.108), and LTP was observed in 21% (10/47) vs. 12% (6/50) (OR 1.9 [95% CI 0.66-5.3], p=0.238) of tumors in the MWA and RFA Group, respectively. Major complications were found in 5 cases (11%) in the MWA Group vs. 2 cases (4%) in RFA, without statistical significance. MWA created larger ablation zones than RFA (p=0.036).Conclusion: MWA and RFA show similar effectiveness and safety in medium-sized liver tumors (1.5-4 cm).