Abstract No. 505 Growing ice: evaluation of change in ice ball size during the second freeze cycle

Abstract

The efficacy of cryoablation in the treatment of renal cell carcinoma (RCC) has been established. Previous studies have noted that the tumoricidal capabilities of cryoablation improve significantly when two freeze/thaw cycles are used. While the manufacturer has provided specifications for predicted ablation zone size, no data is available which evaluates the change in size of the ablation zone between the first and second freeze cycles. The goal of this single-center retrospective review is to evaluate the difference in size of ice ball formation between the first and second freeze cycles. All patients who underwent cryoablation between 2007 and 2017 were retrospectively reviewed. Of the 79 RCC patients second freeze cycle data was available for 11 patients. The patients charts were retrospectively reviewed to ascertain baseline laboratory values, imaging characteristics, and procedural data. The ice ball formation was measured in 3 directions anterior posterior (AP), right-left (RL), and cranial-cauda (CC). Volumes (VL) of the balls were also calculated and percentage changes were calculated by dividing the second ice ball dimensions by the first ice ball dimension and multiplying by 100. The mean size of the first and second freeze cycle ice balls in each direction can be found in Table 1. The change in size was found to be statistically significant in the RL and CC directions (p=0.05 for both), but not the AP direction (p=0.14). The VL was also found to be significantly larger after the second freeze cycle (p=0.01). The mean percentage change between the first and second freeze cycles in the AP, RL, and CC directions were 112%, 117%, and 119% respectively. Ice balls grow significantly bigger during the second freeze cycle; this is important to consider given the potential for injury to adjacent structures.Table 1First Freeze CycleSecond Freeze CycleP ValueAP45.5(10.8)∗48.6(11.2)∗0.14RL32.(6.6)∗36.2(9.4)∗0.05CC31.9(7.4)∗37.7(8.9)∗0.05VL21830(7769)#32292.3(12485)#0.01*mm.#mm3 , ()SD. Open table in a new tab