To investigate
pneumothorax patterns in
pazopanib treatment by focusing on the positional relationship between the visceral pleura and metastatic lung
tumor, we examined 20 patients with advanced soft tissue
tumors who developed lung
metastases and underwent
pazopanib treatment between 2012 and 2019.
Pneumothorax was classified into two types based on the location of the metastatic lesion around the visceral pleural area before
pazopanib treatment: subpleural type, within 5 mm from the pleura; and central type, >5 mm from the pleura. We investigated the rates of
pneumothorax and the associated risk factors. Five patients experienced
pneumothorax (three subpleural and two central types). Cavitation preceded
pneumothorax in 83% of patients and led to connection of the cavitated
cyst of the metastatic lesion to the chest cavity in the shorter term in patients with the subpleural type. Conversely, a more gradual increase in the cavity size and sudden
cyst rupture were observed in the central type. The risk factors for
pneumothorax were cavitation after initiating
pazopanib and intervention before
pazopanib, either ablation or surgery. The location of the metastatic lesions was not a risk factor for the occurrence of
pneumothorax. In conclusion,
pneumothorax is an adverse event associated with
pazopanib treatment. Therefore, attention must be paid to predisposing factors such as the formation of cavitation after
pazopanib initiation and previous interventions to the lungs. Moreover, because subpleural
pneumothorax tends to occur earlier than the central type, a different time course can be anticipated based on the positional relationships of the metastatic lesions to the visceral pleura.