Minimal Ablative Margin as a Key Predictor of Local Tumor Progression After Percutaneous Lung Tumor Ablation

OBJECTIVES: Minimally invasive local therapies such as radiofrequency ablation (RFA), microwave ablation (MWA), and cryoablation (CA) are commonly used to treat malignant lung tumors. This study aimed to identify predictors of local tumor progression (LTP), focusing on the role of minimal ablative margin. METHODS: The medical records of patients ≥ 20 years old with primary or metastatic lung tumors who underwent percutaneous ablation from July 2011 to December 2022 were retrospectively reviewed. Patient demographic information, tumor characteristics, and ablation details were extracted. The primary outcome was LTP, and the key variable of interest was the minimal ablative margin. RESULTS: Seventy-one patients with 88 nodules ablated were included in the analysis, and 22% of the nodules exhibited LTP. In the overall cohort, ROC analysis identified 3 mm as the optimal cut-off for minimal ablative margin to predict LTP. Nodules with margins ≥ 3 mm were associated with significantly higher LTP-free survival at 5 years (82% vs. 23% margins < 3 mm). Kaplan-Meier analysis indicated a significant difference in LTP between ablative margins ≥ 3 and < 3 mm (p < 0.001). RFA was associated with a higher LTP risk than MWA (hazard ratio [HR] = 5.43, 95% confidence interval [CI]: 1.84-16.05), as was a margin < 3 mm (HR = 24.24, 95% CI: 7.66-76.71). CONCLUSIONS: In this cohort, achieving an ablative margin of at least 3 mm was associated with improved LTP-free survival after lung tumor ablation. ADVANCES IN KNOWLEDGE: This threshold should be considered a pragmatic, context-dependent estimate that may require validation across ablation modalities and clinical settings.