A Case of Immune Thrombocytopenia Occurring after Radiotherapy plus Atezolizumab Treatment for Bladder Cancer.

An 84-year-old female developed gross hematuria. She was diagnosed as urinary bladder carcinoma. She was initiated on concurrent atezolizumab plus radiation(a phase Ⅱ clinical trial)(jRCT2031180060). After 8 cycles of atezolizumab, complete response was confirmed. Maintenance atezolizumab treatment was started. Platelet(Plt)count decreased, there was no rechallenge with atezolizumab. Bone marrow examination revealed normal. Plt count recovered. Plt count decreased again. The serum levels of interleukin-6(IL-6)were elevated. She was diagnosed as having immune thrombocytopenia. She was started on treatment with prednisolone(PSL)at dose of 20 mg/day. Plt count was increased.