Meta-analysis of cryoablation versus microwave ablation for small renal masses: is there a difference in outcome?

PURPOSE We aimed to compare local and metastatic recurrence of small renal masses primarily treated by cryoablation or microwave ablation. MATERIALS AND METHODS The MEDLINE, CINAHL, and PUBMED databases were searched to review the treatment of small renal masses with cryoablation or microwave ablation. Fifty-one studies met the inclusion criteria. RESULTS Fifty-one studies representing 3950 kidney lesions were analyzed. No differences were detected in the mean patient age (P = 0.150) or duration of follow-up (P = 0.070). The mean tumor size was significantly larger in the microwave ablation group compared with the cryoablation group (P = 0.030). There was no difference between microwave ablation and cryoablation groups in terms of primary effectiveness (93.75% vs. 91.27%, respectively; P = 0.400), cancer-specific survival (98.27% vs. 96.8%, respectively; P = 0.470), local tumor progression (4.07% vs. 2.53%, respectively; P = 0.460), or progression to metastatic disease (0.8% vs. 0%, respectively; P = 0.120). Patient age was predictive of overall complications in the multivariate analysis (P = 0.020). Local tumor progression with cryoablation was predicted by the mean follow-up duration using univariate (P = 0.009) and multivariate regression (P = 0.003). Clear cell and angiomyolipoma were more frequent in the microwave ablation group (P < 0.0001 and P = 0.03328, respectively), and papillary, chromophobe, and oncocytoma were more frequent in the cryoablation group (P < 0.0001, P < 0.0001, and P = 0.0004, respectively). Open access was used more often in the microwave ablation group than in the cryoablation group (12.20% vs. 1.04%, respectively; P < 0.0001), and percutaneous access was used more frequently in the cryoablation group than in the microwave ablation group (88.64% vs. 37.20%, respectively; P = 0.0021). CONCLUSION There is no difference in local or metastatic recurrence between cryoablation- and microwave ablation-treated small renal masses.