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.