Applying a triple freeze approach to pulmonary cryoablation could safely treat malignant lung tumors with low recurrence and complication rates, New York physician Gray R. Lyons, MD, PhD, and colleagues have reported in the Journal of Vascular and Interventional Radiology.
“Percutaneous image-guided cryoablation of pulmonary tumors is a viable treatment modality for select patients,” Lyons et al. wrote. “Recent reports have demonstrated the efficacy of pulmonary cryoablation in cases of primary lung cancer, recurrent lung cancer and pulmonary metastases. However, these promising findings must be balanced against rates of complications and tumor recurrence.”
Pneumothorax—or a collapsed lung—is among the most common complications, the authors wrote, reaching up to 38 percent occurrence in recent trials. Previous thoracic procedures, gender and an increased number of cryoprobes are all potential contributors to the condition, they said, but little research exists to back those theories.
In newer studies, local tumor recurrence rates after pulmonary cryoablation range from 3 percent to 44 percent—numbers likely influenced by each tumor’s size and distance from major blood vessels.
“To reduce local recurrence rates, a triple freeze protocol has been proposed as a method to increase ablation effectiveness, particularly in the lung, where aerated parenchyma is a poor conductor of thermal energy,” Lyons and co-authors wrote. “Additional freeze-thaw cycles are thought to induce local hemorrhage, which increases conductivity in later cycles via blood products.”
Theoretically, the researchers said, triple freeze protocol could reduce both complication rates and local recurrence rates in patients by minimizing cryoprobe numbers and maximizing the cytotoxic ablation zone. The team tested the method in a study of 42 patients who were treated at the same hospital between 2012 and 2014.
Among the patient pool, a total of 67 nodules underwent treatment with Galil Medical cryoprobes, Lyons and colleagues said. Most nodules—80.6 percent—were metastatic and outside of the pulmonary sphere, while 19.4 percent were pathologically determined to be primary lung malignancies. Tumors were, on average, 1.6 centimeters in diameter.
To achieve the triple freeze approach, the authors followed a routine of a three-minute freeze followed by three minutes of passive thaw, eight minutes of freeze, thee minutes of passive thaw, another eight minutes of freeze and four minutes of active thaw.
Pneumothorax was still the most frequently reported complication during the study, according to the research, but complication rates remained relatively low. Nineteen cases total were affected by pneumothorax, while local tumor recurrence or residual disease occurred in six cases. Recurrence was much more likely in cases where tumors were larger than one centimeter in diameter, with an estimated recurrence rate of up to three years post-ablation.
“Clinically, there is now mounting evidence of the relatively low complication and recurrence rates of triple freeze protocol pulmonary cryoablation,” Lyons et al. wrote. “Further investigation in the relative merits of triple freeze protocol compared with double freeze protocol and other ablative modalities is warranted.”
After graduating from Indiana University-Bloomington with a bachelor’s in journalism, Anicka joined TriMed’s Chicago team in 2017 covering cardiology. Close to her heart is long-form journalism, Pilot G-2 pens, dark chocolate and her dog Harper Lee.