Reply to Homayoun Zargar, Rafael F. Coelho and Jihad H. Kaouk's Letter to the Editor re: R. Houston Thompson, Tom Atwell, Grant Schmit, et al. Comparison of Partial Nephrectomy and Percutaneous Ablation for cT1 Renal Masses. Eur Urol 2015;67:252-9.

We appreciate the insight of Zargar et al [1]. As adapted fromGoldberg et al. [2] andMatin et al. [3], local recurrence was defined in our study as new enhancement of the ablation bed or enlargement of the ablation defect on imaging 3 mo or later following the procedure [4]. In contrast to local recurrence, technical ablation failures (defined as evidence of residual tumor on imaging performed within 3 mo of ablation) were not specifically addressed in the study. We report here that there was a single cT1b cryoablation patient who represented a technical failure. This patient was subsequently managed with a laparoscopic radical nephrectomy. This technical failure notwithstanding, there was a single case of local recurrence after cryoablation in the cT1b cohort 0.7 yr after treatment, and the remaining patients who were followed up had negative imaging during their initial 3-mo surveillance. There were no technical failures in the cT1a radiofrequency ablation and cryoablation groups, and no patient in our study had repeat ablation of a treated tumor within the first 6mo. In addition, wewould like to reiterate that the definition of local recurrence after partial nephrectomy in our article was a new mass in the ipsilateral kidney, irrespective of the location within the kidney [4]. This slightly broader definition of local recurrence for partial nephrectomy patients likely contributed to more events in this group; however, local recurrence-free survival was excellent across the board for these sporadic tumors. Zargar et al [1] also present their unpublished results for cryoablation for 32 T1b renal masses, with estimated 3-yr local recurrence-free survival of 60%, which differs from our result of 97% (or 95% if the technical failure is considered a recurrence event). It is unclear if the results at Cleveland Clinic are for laparoscopic or percutaneous procedures, or represent a combination thereof, and the details of cryoprobe application are not presented. However, all of our ablation patients were initially managed in the urology department with triage of those with anticipated favorable outcomes for ablation. All procedures were performed percutaneously and under general anesthesia, and we believe that general anesthesia facilitates maximum attention to tumor treatment under controlled procedure conditions without discomfort or patient movement. Furthermore, we believe that the percutaneous approach with computed tomography monitoring allows for excellent appreciation of the three-dimensional scope of probe placement and ice ball growth. In addition, we typically utilize the larger-caliber 2.4-mm cryoprobes, which maximize the size of lethal isotherms [5]. We admit that this aggressive treatment of larger renal masses carries a risk of postprocedure bleeding [6], and although beyond the scope of our manuscript, we observe bleeding complications in approximately 8–10% of cryoablation procedures for renal tumors >4 cm. We agree with Zargar et al that longer follow-up is needed and firm conclusions from our manuscript are to be discouraged. This is partly why we concluded that an update to the clinical guidelines would be warranted only if these results were validated. Furthermore, we agree that surgical resection remains the gold standard for cT1b renal masses. In fact, during the study time frame of 2000–2011 at Mayo Clinic Rochester, 326 patients had a partial nephrectomy, 252 patients had a radical nephrectomy, and only 53 ( 8%) patients had cryoablation for cT1b renal tumors.