Risk factors involved in the development of pneumothorax during radiofrequency ablation of lung neoplasms.

Objective: The purpose of this study was to retrospectively evaluate the risk factors involved in the development of pneumothorax during radiofrequency ablation of lung tumors.
Materials and Methods: This retrospective study covered 124 ablation sessions for lung tumors (10 primary lesions, 114 metastatic lesions) in 82 patients (46 men, 36 women; mean age, 64.0 years) treated between December 2005 and January 2008. The exclusion criteria for ablation therapy were lesions with a maximal diameter greater than 5 cm and the presence of more than five lesions. A bipolar electrode needle was used under CT guidance. Four patients were treated with two ablation electrodes simultaneously.
Results: The incidence of pneumothorax (detected with CT) was 11.3% (14 of 124 sessions). Pneumothorax was graded mild (lung surface retraction, < or = 2 cm), moderate (lung surface retraction, 2-4 cm), or severe (lung surface retraction, > or = 4 cm). Significant risk factors encountered in the development of pneumothorax were age greater than 60 years (p = 0.046), emphysema (p = 0.02), tumor diameter < or = 1.5 cm (p = 0.0008), lesions in lower part of lung, (p = 0.027), aerated lung parenchyma traversed by the needle track for a distance > or = 2.6 cm (p = 0.0017), and traversal of a major pulmonary fissure (p = 0.0004). Pneumothorax developed in one of the four patients in whom multiple electrodes were used. The mean depth of lung lesions complicated by pneumothorax was 2.9 +/- 1.55 cm (range, 0-5.5 cm). Conservative treatment was performed in four of the 14 pneumothorax sessions (28.6%). In six of the 14 sessions (42.9%), immediate complete evacuation was achieved with an intercostal catheter and manual evacuation; chest tube placement was indicated in four sessions (28.6%). Two patients were treated with manual evacuation because evidence of a progressive increase in pneumothorax on the 24-hour follow-up CT scan indicated failure of conservative treatment.
Conclusion: The development of pneumothorax complicating radiofrequency ablation can be unpredictable, but the many risk factors involved can make the incidence higher among some patients than others. Some of these risk factors are technically avoidable and have to be ruled out.