Percutaneous Microwave Ablation versus Cryoablation for Small Renal Masses (≤4 cm): 12-Year Experience at a Single Center

-Cryoablation and microwave ablation both provided high technical success and local disease control of cT1a (≤4cm) small renal masses with no significant impact on renal function -Cryoablation lesions at our institution were significantly larger and of greater complexity but cancer specific survival was comparable between the two modalities -Microwave ablation and cryoablation can be viewed as complementary technologies in the kidney, with a lean towards treating smaller, less complex lesions with microwave ablation and larger, more complex lesions with cryoablation Purpose To determine whether microwave ablation (MWA) has equivalent outcomes to cryoablation (CA) in terms of technical success, adverse events, local tumor recurrence and survival in adult patients with solid enhancing renal masses ≤ 4 cm. Materials and Methods A retrospective review of 279 small renal masses (≤ 4cm) in 257 patients (median age: 71 years; range: 40-92) treated with either CA (n=191) or MWA (n=88) between January 2008 and December 2020 at a single, high-volume institution. Evaluations of adverse events, treatment effectiveness, and therapeutic outcomes were conducted for both MWA and CA. Disease-free, metastatic-free, and cancer-specific survival rates were tabulated. The estimated glomerular filtration rate (eGFR) was employed to examine treatment-related alterations in renal function. Results No difference in patient age (p=0.99) or sex (p=0.06) was observed between the MWA and CA groups. Cryoablated lesions were larger (p<0.01) and of greater complexity (p=0.03). The technical success rate for MWA was 100%, whilst one of 191 cryoablated lesions required retreatment for residual tumor. There was no impact on renal function following CA (p=0.76) or MWA (p=0.49). Secondary analysis using propensity score matching demonstrated no significant differences in local recurrence rates (p=0.39), adverse event rates (p=0.20), cancer free survival (p=0.76), or overall survival (p=0.19) when comparing matched cohorts of patients who underwent MWA and CA. Conclusion High technical success and local disease control were achieved for both MWA and CA. Cancer-specific survival was equivalent. Higher adverse event rates following CA may reflect the tendency to treat larger, more complex lesions with CA. To determine whether microwave ablation (MWA) has equivalent outcomes to cryoablation (CA) in terms of technical success, adverse events, local tumor recurrence and survival in adult patients with solid enhancing renal masses ≤ 4 cm. A retrospective review of 279 small renal masses (≤ 4cm) in 257 patients (median age: 71 years; range: 40-92) treated with either CA (n=191) or MWA (n=88) between January 2008 and December 2020 at a single, high-volume institution. Evaluations of adverse events, treatment effectiveness, and therapeutic outcomes were conducted for both MWA and CA. Disease-free, metastatic-free, and cancer-specific survival rates were tabulated. The estimated glomerular filtration rate (eGFR) was employed to examine treatment-related alterations in renal function. No difference in patient age (p=0.99) or sex (p=0.06) was observed between the MWA and CA groups. Cryoablated lesions were larger (p<0.01) and of greater complexity (p=0.03). The technical success rate for MWA was 100%, whilst one of 191 cryoablated lesions required retreatment for residual tumor. There was no impact on renal function following CA (p=0.76) or MWA (p=0.49). Secondary analysis using propensity score matching demonstrated no significant differences in local recurrence rates (p=0.39), adverse event rates (p=0.20), cancer free survival (p=0.76), or overall survival (p=0.19) when comparing matched cohorts of patients who underwent MWA and CA. High technical success and local disease control were achieved for both MWA and CA. Cancer-specific survival was equivalent. Higher adverse event rates following CA may reflect the tendency to treat larger, more complex lesions with CA.