Thermal ablation is now accepted as one of the curative treatments for patients with early-stage hepatocellular carcinoma (HCC), but the efficacy of this treatment for subcapsular HCC is not well characterized. Therefore, we aimed to compare the outcomes of microwave ablation (MWA) and radiofrequency ablation (RFA) for patients with subcapsular HCC.

In total, 195 patients with subcapsular HCC who met the Milan criteria and underwent MWA or RFA were included. Local tumor progression (LTP), overall survival (OS), recurrence beyond the Milan criteria (RBM), and complications of these patients were compared.

After propensity score matching, the 1-, 3-, and 5-year cumulative LTP rates were 6.7%, 9.6%, and 11.4% in the MWA group, and 13.4%, 24.6%, and 29.1% in the RFA group, respectively (p = 0.006). The cumulative rates of RBM were lower in patients treated with MWA than in those treated with RFA (4.4% versus 12% at 1 year; 14.5% versus 23.0% at 3 years; and 37.4% versus 53.9% at 5 years; p = 0.03). The OS rates at 1, 3, and 5 years were 97.1%, 85.9%, and 73.4% in the MWA group, and 95.6%, 80.4%, and 61.4% in the RFA group, respectively (p = 0.36). The rate of major complications showed no significant difference between the MWA group and the RFA group (17.4% vs. 11.6%, p = 0.33).

Compared to RFA, MWA showed better tumor control for subcapsular HCC within the Milan criteria. There was no difference in the incidence of major complications between the two groups.