Optimizing the Protocol for Pulmonary Cryoablation: A Comparison of a Dual- and Triple-Freeze Protocol

Abstract

The purpose of this study was to compare a double freeze–thaw protocol to a triple freeze–thaw protocol for pulmonary cryoablation utilizing an in vivo porcine lung model. A total of 18 cryoablations were performed in normal porcine lung utilizing percutaneous technique with 9 each in a double- (10-5-10) and triple-freeze (3-3-7-7-5) protocol. Serial noncontrast CT images were obtained during the ablation. CT imaging findings and pathology were reviewed. No imaging changes were identified during the initial freeze cycle with either protocol. However, during the first thaw cycle, a region of ground glass opacity developed around the probe with both protocols. Because the initial freeze was shorter with the triple freeze–thaw protocol, the imaging findings were apparent sooner with this protocol (6 vs. 13 min). Also, despite a shorter total freeze time (15 vs. 20 min), the ablation zone identified with the triple freeze–thaw protocol was not significantly different from the double freeze–thaw protocol (mean diameter: 1.67 ± 0.41 cm vs. 1.66 ± 0.21 cm, P = 0.77; area: 2.1 ± 0.48 cm2 vs. 1.99 ± 0.62 cm2, P = 0.7; and circularity: 0.95 ± 0.04 vs. 0.96 ± 0.03, P = 0.62, respectively). This study suggests that there may be several advantages of a triple freeze–thaw protocol for pulmonary cryoablation, including earlier identification of the imaging findings associated with the ablation, the promise of a shorter procedure time or larger zones of ablation, and theoretically, more effective cytotoxicity related to the additional freeze–thaw cycle.

CT-guided percutaneous cryoablation of central lung tumors

“…One study showed that double-and triple-freeze protocols provided comparable ablation zones in a porcine model but the triple-freeze protocol resulted in earlier visualization of the ice ball. Therefore, a triple-freeze protocol may allow more effective intraprocedural ice ball monitoring in the future (28).…”

“…The marked and rapid improvement seen on MRI and CT after 24 hours suggests that the peritumoral lung opacification is predominantly due to hemorrhagic edema. In addition to allowing visualization of the ice ball, peritumoral lung opacification also increases thermal conductivity of lung tissue and allows for more rapid freezing and possibly larger ablation zones (28). Based on these observations, some authors have suggested an initial short freeze to create peritumoral opacification followed by two additional freezes to treat the tumor (20,21,23).…”

“…Prior reports have focused on the feasibility, safety, and local control rate of CT-guided cryoablation of lung tumors in general; however, these reports provided no detailed information regarding tumor location and did not discuss the issues relevant to the treatment of central tumors (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31). Wang et al (19) placed straight cryoablation applicators into tumors tandem to a guidance needle outside the CT gantry, as their CT gantry could not accommodate the entire length of straight cryoablation applicators.…”

“…Heat-based ablation methods may not be safe in the treatment of central lung tumors because of a possibility of bronchial disruption or perforation, which may result in bronchopleural fistula formation (19). Although cryoablation has been used to treat lung malignancies (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31), there are limited data on the safety and effectiveness of percutaneous cryoablation of central lung tumors. In this study, we describe our experience with CT-guided percutaneous cryoablation of central lung tumors and the role of ice ball monitoring.…”

Non-extended cryoablation could be a new strategy in lung cancer management: An experiment on green fluorescent protein-labeled Lewis lung cancer-bearing mice

“…However, the explorers argued that, in their clinical experience, non-extended cryoablation could contain the development of the primary tumor for a long time with less intraoperative and postoperative risks, and patients could have higher quality of life in the whole process. Although several animal researches have been done in order to answer the questions and optimize the procedure, the common limitation of these studies was that the experiments were done on normal lung tissues rather than lung cancer-bearing models [9,16,27,29]. The answer to this controversy was still in suspense for both sides lacking of stronger evidence [30,38].…”