Risk Factors Invoived In The Development Of Pneumothorax During Microwave Ablation Of Lung Neoplasms

Background and Objective:Percutaneous thermal ablation has been proved to be effective in treating primary and metastatic lung tumors. The most widely used technique is radiofrequency ablation (RFA) and microwave ablation (MWA). MWA can produce high temperatures above 60℃ in a short time, leading to coagulation necrosis of the cells, via water molecules, protein molecules and other polar molecules within tumor tissue vibrating at a high speed. As compared with RFA, MWA used in the lung neoplasma has some advantages, including higher and faster energy convection, a larger ablation zone and a lower heatsink effect. MWA in common with RFA therapy can lead to some regular complications. These include post-ablation syndrome, pneumothorax, pleural effusion, bleeding, and infection. Pneumothorax is the most frequent complication. Chest tube placement is required for severe pneumothorax and results in prolonged hospitalization and additional expense. Adequate assessment of the risk factors that contribute to the development of pneumothorax is essential to the minimization of its incidence. The purpose of our study was to retrospectively determine the frequency of complicating pneumothorax and the risk factors associated with the development of pneumothorax during MWA of pulmonary neoplasms.Methods:The study comprised 324 consecutive MWA ablation sessions that were performed at our institution from January 2013 to September 2014. To determine underlying contributing factors to the pneumothorax. we assessed the factors as follow.1. Patient related factors:sex, age, score of PS, smoking history, weight loss, emphysema, chronic diseases (including hypertension, CHD, diabetes), history of lung surgery, Previous radiotherapy, previous chemotherapy, lung function.2. Patient-and tumor-related factors:primary or metastatic, tumor size, tumor location(right vs. left, upper vs. middle and lower), distance to the nearest pleura, No. of tumors ablated.3. MWA procedure-related factors:patient position (prone vs. supine), distance to the skin along the track, length of aerated lung traversed by the antenna, total ablation time, biopsy, No. of punctures, traversal of major pulmonary fissure, GGO after ablation contacting pleura, GGO after ablation contacting puncture point of pleura.Repeat ablation sessions were considered to be independent, and analyses were performed by using sessions as the sampling unit (324 sessions). The sessions were divided into groups according to the occurrence of pneumothorax and placement of chest tube. Groups were defined as patients with or those without pneumothorax and patients with or those without chest tube placement for pneumothorax. Each factor was compared between groups by using a univariate analysis. Multivariable analysis using logistic regression was performed for various factors related to pneumothorax and placement of chest tube. A p value of less than 0.05 was considered to be statistically significant in all analyses. Statistical analysis was performed using SPSS 17.0 (SPSS, Inc, Chicago, IL).Results:1. Pneumothorax occurred after 152 (46.91%) of 324 sessions,.Of the 152 cases of pneumothorax,45 (29.6%) necessitated chest tube placement, which was correspondent to 13.9%(45 of 224 sessions) across all sessions.23 of 152 sessions (7.09%) were complicated by delayed pneumothorax.23 of 152 sessions (7.09%) were complicated by delayed pneumothorax. Bronchopleural fistulas after MWA occurred in 3 of 152 sessions (1.97%).52 of 152 sessions (34.21%)were complicated by subcutaneous emphysema.2. In the univariate statistical analysis of variables, the risk of pneumothorax was strongly correlated with smoking history, emphysema, no history of lung surgery, length of aerated lung traversed by the antenna, No. of punctures, traversal of major pulmonary fissure and lung function(FEV1/FVC%, TLCO%, VA, TLCO/VA, TLCO/VA%, VR%). Multivariable analysis indicated that emphysema, no history of lung surgery, length of aerated lung traversed by the antenna, No. of punctures and traversal of major pulmonary fissure were the independent risk factors related to pneumothorax.3. In the univariate statistical analysis of variables, the risk of chest tube placement was strongly correlated with smoking history, emphysema, position(supine), length of aerated lung traversed by the antenna, traversal of major pulmonary fissure and lung function(FEV1/FVC%, TLCO%, VA, TLCO/VA, TLCO/VA%, VR%). Multivariable analysis indicated that emphysema, ength of aerated lung traversed by the antenna and traversal of major pulmonary fissure were the independent risk factors related to chest tube placement.Conclusions:1. Pneumothorax is the most frequent complication with MWA of lung tumors. Chest tube placement is required for severe or progressive pneumothorax.2. High risk factors of the pneumothroax:smoking history, emphysema, no history of lung surgery, length of aerated lung traversed by the antenna, No. of punctures and traversal of major pulmonary fissure. Independent risk factors:emphysema, no history of lung surgery, length of aerated lung traversed by the antenna, No. of punctures and traversal of major pulmonary fissure.3. High risk factors of chest tube placement:smoking history, emphysema, position (supine), length of aerated lung traversed by the antenna, traversal of major pulmonary fissure, FEV1/FVC%, TLCO%, VA, TLCO/VA, TLCO/VA% and VR%. Independent risk factors:emphysema, ength of aerated lung traversed by the antenna and traversal of major pulmonary fissure.