Autoimmune encephalitis induced by atezolizumab and bevacizumab therapy for advanced hepatocellular carcinoma: a case report

Atezolizumab, an immune checkpoint inhibitor (ICI), became available for treating hepatocellular carcinoma (HCC) in 2020. It is now widely used in combination with bevacizumab for advanced HCC. However, ICI has been reported to cause severe immune-related adverse events (irAEs), and reports in the treatment of HCC are still very rare. We report a case of autoimmune encephalitis as an irAE in a patient undergoing ICI therapy for HCC. A 66-year-old Japanese man was diagnosed with multiple HCC in the parenchyma of both liver lobes. We initiated combination treatment with atezolizumab and bevacizumab. On day 8, the patient had symptoms of fever, diarrhea, and loss of appetite and was transferred to our hospital due to impaired consciousness on day 10. He was restless and incoherent. Analysis of cerebrospinal fluid revealed an elevated monocyte count. The patient was diagnosed with autoimmune encephalitis due to ICI and started treatment with methylprednisolone 1,000 mg for 3 days. On the second day of treatment, his consciousness improved dramatically, and he was discharged on day 13. The frequency of ICI therapy will increase; therefore, it is necessary to understand the rare irAEs due to ICIs. Moreover, prompt diagnosis and early administration of steroids may contribute to a successful response.