Radiofrequency Ablation of Small Lung Metastases by a Single Application of a 2-cm Expandable Electrode: Determination of Favorable Responders

Purpose: To determine which lung metastases are most likely to be treated effectively with a single radiofrequency (RF) application (defined as two separate applications of RF energy at a single electrode position) with a multitined expandable electrode with arrays 2 cm in diameter. Materials and Methods: The authors retrospectively evaluated 88 lung metastases (mean long-axis diameter, 0.9 cm) in 36 patients (20 men and 16 women; mean age, 57 years) treated with a single RF application with a multitined expandable electrode with arrays 2 cm in diameter. Based on follow-up computed tomographic examinations, the technique effectiveness rates were estimated with Kaplan-Meier analysis. Multiple variables were analyzed with the log-rank test to determine risk factors for local progression. Then, the technique effectiveness rates were again estimated when considering only metastases without risk factors and compared with those of other tumors. Results: The median follow-up period was 13.2 months (range, 6.0-24.7 months). Tumor size greater than 1.0 cm (P = .033) and contact with the bronchus with an inner diameter of at least 2 mm (P = .047) were the significant risk factors for local progression. The technique effectiveness rates for metastases 1.0 cm or smaller that were not in contact with the bronchus (n = 59) were 96% at 1 year and at 2 years; those rates were significantly (P = .010) higher than those in other tumors (n = 29). Conclusions: A single RF application with a multitined expandable electrode with arrays 2 cm in diameter is most likely to suffice in small (≤1 cm) lung metastases not in contact with a bronchus.