Although not statistically significant, LOS was lower by 0.4 days with MWA compared with RFA based on seven observational studies (WMD=−0.40 days; P=0.26) (Table 2, Figure S11).
The main reported complications for both study groups included bleeding, hematoma, portal vein thrombosis, pleural effusions, pneumothorax, ascites, infections, and fever. The risk of complications was not significantly different between MWA and RFA overall (RR=1.05; P=0.75) or for the four RCTs (RR=0.84; P=0.68) (Table 2, Figure 4, Figure S12).
Results showed that there were no statistically significant differences between MWA and RFA regardless of tumor size for one-year OS, complications, and technique efficacy outcomes (Table 3). However, for the outcome of LTP, MWA was associated with a significant reduction of 37% (RR=0.63; P=0.001) compared with RFA, among patients with tumor sizes ≥2.5 cm (Table 3).
(To view a larger version of Table 3, click here.)
No statistically significant differences were reported between MWA and RFA for complications and technique efficacy regardless of tumor type (Table 3). However, LTP was statistically significantly reduced by 33% with MWA compared with RFA among patients with HCC (RR=0.67; P<0.001). Although LTP was also lower in patients with liver metastasis with MWA versus RFA, the difference was not significant (RR=0.71; P=0.61). Also, among patients with liver metastasis, MWA was associated with lower survival at one-year compared with MWA (RR=0.90; P=0.04); however, differences were not statistically significant in HCC patients (RR=1.00; P=0.87). (Table 3).
There were no significant differences between MWA and RFA for one-year OS, complications, and technique efficacy, regardless of whether TACE was added to ablation treatment arms or not. For LTP, MWA was associated with a lower risk compared with RFA for both comparisons; however, results were only significant for the comparison of MWA and RFA only (RR=0.72; P=0.02) (Table 3).
For the outcomes of one-year OS, complications, and technique efficacy, there were no significant differences between MWA and RFA, irrespective of MWA frequency. For LTP, the 2450 MHz MWA frequency was associated with a significant reduction of 33% compared with RFA (RR=0.67; P<0.001); however, the 915 MHz MWA frequency was associated with an increase in the risk of LTP (RR=1.79; P=0.01) (Table 3).
Results of sensitivity analyses on alternative methods (ie, fixed-effects model), study quality (ie, exclusion of poor-quality studies), and surgery type (ie, exclusion of studies involving open surgery23,25,44) were similar in magnitude and direction to the main analysis with some exceptions. MWA was associated with a significant reduction in LTP for all sensitivity analyses. Additionally, when fixed-effects models were used instead of the random-effects model, MWA was associated with significant improvements in technique efficacy (RR=1.02; P=0.04), reductions in EHM (RR=0.64; P<0.05), and hospital LOS (WMD=−0.27 days; P<0.05) compared with RFA. The results of the meta-analysis were not sensitive to the exclusion of studies involving open surgery (Table 4).
(To view a larger version of Table 4, click here.)
Outcomes reported by ≥10 studies (LTP, technique efficacy, one- and three-year OS, and complications) were examined for publication bias using funnel plots. Results demonstrated a low risk of publication bias for the outcomes assessed. The funnel plot for LTP is presented in Figure 5, and those for technique efficacy, one- and three-year OS, and complications are presented in Figure S13.
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