Clinical Outcomes and Techniques for Radiofrequency Ablation of Lung Tumors Smaller than 1 cm.

Purpose: To evaluate the outcomes of radiofrequency ablation (RFA) on lung tumors < 1 cm in maximum diameter. Materials and Methods: Twenty-eight patients (12 male, 16 female; median age, 59 years; mean age, 58 ± 16 years; range, 16-78 years) who underwent RFA for lung tumors < 1 cm in diameter between November 2009 and September 2018 were included in this study. Thirty-five tumors (median size, 8.4 mm; mean size, 7.7 ± 1.9 mm; range, 3.6-9.9 mm) were treated with 33 sessions of RFA. Technique efficacy and safety were subsequently evaluated. Initial and secondary technique efficacy were defined as complete ablation without residual tumor or local tumor progression after initial and repeat RFA, respectively. Safety was evaluated according to the Common Terminology Criteria for Adverse Events, version 5.0. Results: Residual tumor remained for 1 tumor (3%, 1/35) and local tumor progression was found in 2 tumors (6%, 2/35). Initial technique efficacy rate was therefore 91% (32/35). The remaining 3 tumors were treated by repeat RFA (secondary technique efficacy rate: 100%, 35/35). Initial technique efficacy rate was significantly lower for tumors treated with starting energy ≥ 20 W (P = 0.02) and showing a quick increase in tissue impedance (P = 0.01). There were 4 grade 2 adverse events (12%, 4/33) comprising pneumothorax requiring chest tube placement, and 14 grade 1 adverse events comprising self-limiting pneumothorax (36%, 12/33) and pulmonary parenchymal hemorrhage (6%, 2/33). Conclusion: To achieve good outcomes for lung tumors < 1 cm, radiofrequency energy should be started at < 20 W. Application of manual mode ablation might be considered when delivery of power cannot be continued due to a quick increase in tissue impedance.