Risk factors associated with complications and local tumour progression in image-guided triple-freezing cryoablation for lung tumour: a longitudinal study.

[PURPOSE] This study aimed to investigate the efficacy of triple-freezing cryoablation, the temporal changes of ablation zones, and their association with local tumor progression in patients with lung malignancy.

[METHODS] This retrospective analysis included patients who underwent triple-freezing cryoablation for lung tumors between 2009 and 2017. The size, shape of the ablation zones, and procedure related complications were evaluated. Fine-Gray regression analysis was utilized to determine the risk factors associated with recurrence while considering mortality as a competing risk.

[RESULTS] The study included 41 patients, with 58 ablation sessions for 76 lesions. A tumor size >2 cm was associated with a higher rate of local tumor progression (subdistribution hazard ratio [SHR], 2.623, 95% CI, 1.126-6.107,  = 0.025). An ablation zone-tumor ratio ≥2 emerged as an independent predictor of less local tumor progression (SHR, 0.384, 95% confidence interval [CI]; 0.168-0.877;  = 0.023). There was a 1.7% incidence of adverse events classified as CTCAE (v5.0) grade 3 or higher. Patients without subsequent local tumor progression showed a greater decrease in the ablation zone minor axis at the 6 month-follow up computed tomography (CT) than those with recurrence (25.8% decrease [interquartile range (IQR), 10.3-47.5%] vs 2.4% decrease [IQR, -10.0-7.9%];  = 0.004).

[CONCLUSION] An ablation zone-tumor ratio of ≥2 was associated with less local tumor progression, and a smaller decrease in the ablation zone at the 6-month follow-up CT indicated a higher rate of subsequent local tumor progression.