LAUSR

Radiofrequency ablation (RFA) demonstrates similar overall survival (OS) and progression-free survival (PFS) compared to surgery in the treatment of solitary or multiple small size lung metastases [1, 2]. RFA should be as minimally invasive as possible, and reducing chest tube insertion probably helps. However, as interventional radiologist, we should not make a rod for our own back. When surgeons have 100% chest tube insertion after lung resection, none is reported as adverse events. Pneumothorax must probably not be reported as complication of the treatment or even not as adverse events as far as it does not modify hospital stay and post-treatment care. Having said that, it is of course important to limit pneumothoraces and chest tube insertion induced by thermal ablation. In this issue of CVIR, Dassa et al. report on efficacy of tract embolization after percutaneous pulmonary radiofrequency ablation using gelatin sponge slurry with iodinated contrast medium [3]. This clinical work is following animal experiment by the same group that demonstrated the pathological substratum for increased rate of pneumothorax during RFA versus biopsy to be a fistulous tract between ablation zone and pleura along needle shaft, and different from post-biopsy pneumothorax where no fistulous tract is observed [4]. These results obtained in animal experiment were confirmed by clinical observation [5]. Dassa et al. publication reports (gelatin sponge slurry with iodinated contrast medium) GSSI to reduce the incidence of pneumothorax twofold (62% vs 34%) and incidence of chest tube placement threefold (29% vs 10%) which results in shorter duration of hospital stay. However, for lung thermal ablation we are lacking studies evaluating in details all parameters that may favor pneumothorax, such as patients positioning during and after ablation, type of ventilation, type of thermal ablation and consequently prevention of pneumothorax has probably much more facets than the use tract sealant. A systematic review and meta-analysis among 7080 patients revealed normal saline tract sealant to reduce chest drain insertion ninefold. Rapid rollover maneuver to puncture site down, tract plug or blood patch to each reduce chest tube insertion by threefold [6]. Deep expiration and breath-hold on needle extraction has been also advocated to help reduce pneumothorax and chest drain insertions following lung biopsies [6]. Less data exists on post-RFA pneumothoraces with the length of the electrode trajectory through aerated lung and a greater number of tumors ablated being the most commonly reported factors to favor pneumothorax and chest tube insertion [7, 8], but there is no substantial report on parameters such patient positioning. For preventing pneumothorax occurrence, Dassa et al. used GSSI which can be questionable as an embolic agent. Indeed, when injected directly into the lung needle tract there is a possible risk of injection in pulmonary veins and then migration into major visceral artery. More data are needed to assess safety. Saline might be safer and maybe as efficient. Dedicated plugs are an interesting option to clinically validated options as lung ablation has extended beyond RFA to MWA using larger caliber antennas, or to cryoablation using several probes [9, 10]. At last, rare but major complications, such as air embolism, might benefit from countermeasures to pneumothorax, such as placing target tumor and needle tract below the left atrium: & Thierry de Baère [email protected]