Risk factors for local tumor progression after RFA of pulmonary metastases: a matched case-control study

Objectives Curative treatment of oligometastatic pulmonary disease aims at eradication of all metastases. Radiofrequency ablation (RFA) has been shown to be an efficient method and the frequency of local tumor progression (LTP) should be minimized. The objective of this study was to determine the morphological and treatment-related risk factors for LTP after RFA of pulmonary metastases. Materials and methods All patients treated with RFA for pulmonary metastases from 2002 to 2014 were reviewed. All LTPs from 2011 to 2014 were individually matched on the basis of tumor size, number, and histology. In total, 48 LTPs and 112 controls were blindly analyzed for morphological factors including vicinity of bronchus and vessels as well as treatment-related factors such as the size of the ablation zone and ablation margins. Results In the simple regression analysis, the significant predictive variables were <= 5-mm distance to a large bronchus (OR = 4.94; p = 0.0095) or large vessel (OR = 7.09; p < 0.001), minimal ablation margin (<= 5 mm (OR = 42.67; p < 0.001), and a central-peripheral ablation offset/ablation zone size > 0.36 (OR = 13.83; p = 0.013). In the multiple regression model, only a minimal ablation margin <= 5 mm remained a significant risk factor for LTP. Conclusion Only the minimal ablation margin remains significant in the multiple regression analysis; the other factors are presumably surrogates of an insufficient ablation margin. Improvement of lung RFA outcomes can probably be obtained by immediate post RFA evaluation of ablation margins to ensure a minimal ablation margin of at least 5 mm.

Automated summary

This study identified significant predictive variables for local tumor progression (LTP) after RFA of pulmonary metastases, including factors such as proximity to large bronchi or vessels, minimal ablation margin, and central-peripheral ablation offset/ablation zone size. In the multiple regression model, only a minimal ablation margin <= 5 mm remained a significant risk factor for LTP. Immediate post-RFA evaluation of ablation margins to ensure a minimal ablation margin of at least 5 mm may lead to improved lung RFA outcomes.