Clinical features and outcomes of atezolizumab-associated encephalitis

Abstract

To explore the clinical characteristics of atezolizumab-associated encephalitis and to provide clinical evidence for diagnosis and treatment. Clinical reports on atezolizumab-associated encephalitis published before June 30, 2026 were collected for retrospective analysis by searching Chinese and English databases. A total of 39 cases of encephalitis were included, with a median age of 60 years (33, 78). The median time of symptom onset was 14 days (2, 420) after the initial administration. Fever (53.8%), confusion (51.3%) and headache (28.2%) were the main complaints of the patients. Cerebrospinal fluid examination showed elevated white blood cell count and protein, with median values of 27 cells/μL (1, 553) and 133mg/dL (27.1, 815), respectively. Brain magnetic resonance imaging showed T2 fluid-attenuated inversion recovery hyperintensities in half of the patients. Electroencephalogram showed display epileptiform discharges (26.7%) and slow waves (40.0%). After discontinuation of atezolizumab and initiation of targeted treatment, 97.4% of patients achieved symptomatic improvement or recovery, while 2.6% died of encephalitis-related complications. Patients with atezolizumab-associated encephalitis were predominantly middle-aged and elderly, with fever, confusion and headache as the major manifestations. Clinicians should be alert to the potential risk of encephalitis during atezolizumab treatment. Most patients obtained symptom relief or clinical recovery following atezolizumab discontinuation and treatment; only a few succumbed to severe encephalitis-related complications.