Association of CT characteristics of osteosarcoma lung metastases with spontaneous pneumothorax: a retrospective analysis

Background: Spontaneous pneumothorax (SP) has been reported to be associated with osteosarcoma lung metastases, but the computed tomography (CT) characteristics of lung metastases in patients with pneumothorax have not been comprehensively described. The study aimed to describe the CT characteristics of lung metastases in patients with osteosarcoma and to identify factors associated with SP. Methods: This study comprised 123 patients diagnosed with osteosarcoma lung metastasis at our hospital between January 2016 and December 2021. Demographics, tumor characteristics at initial diagnosis, the time interval between diagnosis of lung metastases and pneumothorax, and features of lung metastases on chest CT were documented. Results: A total of 31 patients experienced SP (20 unilateral and 11 bilateral cases). Lung metastases were identified as multiple nodules or masses (39/42 vs. 123/204, P<0.001), with higher rates of cavitation and pleural involvement (23/42 vs. 19/178, P<0.001 and 38/42 vs. 63/178, P<0.001, respectively) in patients with pneumothorax. A considerable prevalence of calcification (123/220) was observed in lung metastases. However, no statistically significant difference was found between patients with and without pneumothorax. The duration of detection of lung metastases was shorter in patients with pneumothorax than in those without it (6 vs. 11 months, P=0.039). Binary logistic regression analysis revealed that only the presence of cavitation and pleural involvement of lung metastases were significantly associated with pneumothorax, with odds ratios of 12.430 [95% confidence interval (CI): 3.011-51.320; P<0.001] and 15.480 (95% CI: 4.038-59.348; P<0.001), respectively. Conclusions: SP can occur in the region of lung metastases near the pleura following the formation and bursting of cavities. Regular follow-up of these patients has the potential to ensure early detection and treatment of pneumothorax.