Letter: is microwave ablation superior to radiofrequency ablation for early-stage hepatocellular carcinoma?

Microwave ablation (MWA) and radiofrequency ablation (RFA) are two main curative therapies for early-stage hepatocellular carcinoma (HCC). The indications for MWA and RFA are similar, namely, size less than 3 cm, up to three lesions, and the absence of extrahepatic disease. However, the therapeutic effect of MWA and RFA are different. MWA uses an electromagnetic field while RFA uses an electrical current.1 In the past decade, many studies comparing the safety and efficacy of MWA and RFA for early-stage HCC were reported.2-9 Almost all of them found that MWA and RFA provided similar outcomes.2-9

However, the recent interesting retrospective study by Liu and coworkers10 had different findings. This study included 126 patients who underwent MWA and 436 who underwent RFA. The MWA group had heavier tumour burden, lower serum albumin level, higher alanine aminotransferase level, higher aspartate aminotransferase level and longer prothrombin time. However, patients in the MVA group had slightly higher overall survival and statistically significant higher recurrence-free survival after a median follow-up duration of 36.8 and 34.1 months for the corresponding groups.

In order to reveal which treatment modality is more useful in patients’ outcomes in a real-world study, we systematically searched the PubMed database for studies comparing MWA and RFA for early-stage HCC. Only randomised controlled trials or studies with comparable baseline variables (all P > 0.05) were included. A retrospective study with propensity score analysis was also included. In this case, only data after propensity score matching were included. A P value by log-rank test on overall survival and recurrence-free survival was extracted from original studies. Risk ratios (RRs) and 95% confidence intervals (95% CIs) were calculated to compare the efficacy of MWA and RFA for early-stage HCC. Eight studies involving 991 patients who underwent MWA and 816 patients who underwent RFA were included in the analysis (Table 1). All included studies had comparable baseline variables. Only the study by Liu and coworkers10 found that MWA was obviously superior to RFA, with statistically significantly higher overall survival and recurrence-free survival after propensity score analysis. However, the study by Ohmoto and coworkers5 revealed a contrary result. Other six studies found that MWA was associated with a similar overall survival and/or recurrence-free survival with RFA.3, 4, 6-9 Pooled results of the eight studies revealed that patients in the RFA group had a statistically significantly higher 1-year overall survival than those in the MWA group (RR 1.74, 95% CI 1.10-2.75, P = 0.02). However, patients in the two groups had similar 2-years (RR 0.98, 95% CI 0.74-1.31, P = 0.91) and 3-years overall survival (RR 0.96, 95% CI 0.79-1.16, P = 0.65). When only the three randomised controlled trials were analysed, results were not altered. For 1, 2, and 3 years of recurrence-free survival, the two groups showed similar results.

In conclusion, MWA may not be superior to RFA for early-stage HCC in terms of overall survival and recurrence-free survival in the real world.

FUNDING INFORMATION

This work was supported by the Self-Raised Scientific Research Fund of the Ministry of Health of Guangxi Province (Z2013430 and Z2016479) and the Graduate Course Construction Project of Guangxi Medical University (YJSA2017014). The funding source had no role in the design or conduct of the study; in the collection, analysis, or interpretation of the data; or in the preparation, review, or approval of the manuscript.