Secondary pneumothorax during immunotherapy in two patients with metastatic solid tumors; a new entity.

Background: We present two cases of secondary pneumothorax after immunotherapy in two different clinics. Case summary: A 25-year old female patient with metastatic osteosarcoma, treated with atezolizumab. Grade 2 pneumonitis developed twice in the first year. Treatment was continued after recovery and areas of pneumonitis and pneumothorax were observed on computed tomography. No other reason could be found to cause pneumothorax. Pneumothorax resorbed spontaneously during follow-up. A 36-year old female patient treated with nivolumab for metastatic renal cell carcinoma (RCC), areas of pneumonitis and pneumothorax were only found as the cause of dyspnea. After treatment, remission was achieved on computed tomography findings. Pneumothorax was detected for the second time during continued therapy, and immunotherapy stopped permanently. Conclusion: These cases, indicate that immunotherapy can cause secondary immune-related pneumothorax based on immune pneumonitis.