The clinical benefits of immune checkpoint inhibitors for thymic carcinomas

Aim and Objectives: Thymic carcinomas arise in the anterior mediastinum. The Masaoka staging system has been widely used for staging thymic carcinomas and most patients with them are diagnosed as being at high clinical stages due to the aggressiveness nature. In such cases, chemotherapy is the primary treatment modality. However, its effect on tumours are limited and a standard chemotherapy regimen has not been established. Recently, immune checkpoint inhibitors have changed conventional chemotherapy regimen due to their effectiveness against various types of cancers. The effects of these inhibitors on thymic carcinomas are unknown because any immunotherapy has not been approved for them. Patients and Case Presentation: We administered nivolumab, anti-Programmed Cell Death (PD)-1 antibody, to four patients with unresectable thymic carcinomas who had previously undergone conventional chemotherapy. A histopathology on tumours from these patients revealed the presence of squamous cell carcinoma and PD-L1 expression. After treatment with nivolumab, all patients showed improvements. Three patients showed partial improvements as observed in computed tomography images, and the tumour biomarkers of the fourth patient was decreased although radiological evaluation showed stable disease. None of them experienced severe immune-related adverse events. Conclusions: Although large clinical trials for the evaluation of immune checkpoint inhibitors for the treatment of thymic carcinoma are necessary, our results suggest the potential benefits of using these inhibitors to treat thymic carcinomas.