Simultaneous tumor shrinkage and bronchial perforation induced by nivolumab plus cabozantinib combination therapy in a patient with collecting duct carcinoma.

Vascular endothelial growth factor receptor tyrosine kinase inhibitors are known to cause perforation as one of its severe side effects, and postoperative and post-radiation therapy are known risk factors. However, there are few studies on perforation following tumor shrinkage. A 78-year-old woman with postoperative recurring left collecting duct carcinoma of the right hilar lymph nodes and mediastinum underwent eight courses of nivolumab plus cabozantinib, resulting in tumor shrinkage. Three days after the last administration, she developed fever and cough and was hospitalized for right lobar pneumonia. The patient received long-term antibiotics for bronchial fistula with the destruction of the bronchial wall and secondary lung abscess. When using nivolumab plus cabozantinib combination therapy for a tumor with bronchial invasion, physicians should be aware of bronchial perforation as the tumor shrinks.