Primary mechanisms have been proposed to explain spontaneous secondary pneumothorax in patients with pulmonary metastasis . Therapy-related tumor necrosis of subpleural nodules with bronchopleural fistula formation is the most likely mechanism. Secondary therapy-related refractory pneumothorax may increase because of the dramatic response by molecular targeted therapies. In one study, the development of pneumothorax associated with the use of axitinib was reported to have occurred in 4 (1.1%) of 359 RCC patients that had received axitinib .
The volume of PFP we obtained was sufficient to fill the cavity, and we attempted not only to cover the orifice but also to fill the cavity completely. Therefore, we named this method “fat pad plombage.” An air space developed in the bottom of the cavity after surgery probably because of ventilation; therefore, the PFP should be fixed on the bottom through suturing. Although the efficacy of free PFP for sealing intraoperative alveolar air leaks has been reported [4, 5], usefulness of PFP to seal a large pulmonary bronchopleural fistula causing refractory pneumothorax, as observed in our case, has not been reported. In this case, we used pedicled PFP; however, free PFP is also thought to be useful. Indeed, the use of PFP in previous reports as a sealant for preventing alveolar air leaks was not pedicled but free [4, 5]. If the cavity and fistula were apart from the anterior mediastinum and pedicled PFP was not reachable, free PFP would be chosen. In our case, bronchial occlusion with EWS before surgery could not stop air leakage completely; however, it might play a role in the success of treatment by reduction of massive leakage. EWS occlusion prior to the surgery may be a strategy to treat similar cases.
Reportedly, PFP produces neovascularization in chick chorioallantoic membranes and cytokines related to tissue repair, such as interleukin-1α and interleukin-1β, tumor necrosis factor-α, and interleukin-6 . Pedicled PFP may be more beneficial than free PFP since angiogenesis of the cavity wall might be inhibited by axitinib in our case. No infection around the fistula was observed in our case. We have enough data to assess whether or not this method can be used in infectious cases. Although early atrophy of the fat pad may occur, the usefulness of free subcutaneous fat pads as a sealant for alveolar air leakage was confirmed on CT performed 6 months after surgery . In addition, histologic examination showed that the fat structure was maintained 1 month after surgery, although the feeding vessel to the fat mass was not observed in a canine model . In our case, the follow-up period was insufficient, and a longer follow-up is preferable to assess our method. Further accumulation of cases is necessary to evaluate the validity of this method.