Case Report of Immuno-Oncotherapy (IO) Provoked Encephalitis Mimicking Brain Metastasis in a Patient with History of Traumatic Brain Injury

Abstract

Background: Immuno-oncotherapy (IO) has revolutionized systemic cancer care but remains experimental in brain tumors. IO treatment risks multiorgan autoimmune inflammatory responses that limit its use. The central nervous system (CNS) is an immune-specialized compartment with restricted cellular access, thus fewer cases are reported for immune-mediated encephalitis. Interestingly, patients with history of blood-brain barrier compromise are potentially at higher risk for immune cell trafficking to the CNS.

Case description: We report the first case, to our knowledge, of a 70-year-old man with clear cell renal cell carcinoma with pulmonary metastases treated with lung irradiation, nephrectomy, and chemotherapy prior to switching to single-agent nivolumab IO. The patient presented with new-onset generalized tonic-clonic seizure and left visual field-cut. Review of patient history revealed remote traumatic brain injury (TBI). Brain imaging noted a solid-enhancing right occipital mass that was presumed metastasis versus lymphoma. Cerebrospinal fluid cytology was negative for malignancy but concerning for lymphoproliferative process not determined to be malignant. The patient started steroids and anti-epileptic therapy. After negative systemic cancer re-staging, IO was discontinued and steroids were initiated with demonstrated patient clinical improvement.

Conclusions: We concluded the diagnosis of immune-mediated encephalitis secondary to IO with collection of reactive T-cells within the area of encephalomalacia. The area of encephalomalacia from prior TBI served to compartmentalize the reactive lymphocytes, giving the appearance of a mass. Taken together, new onset seizure in patients on IO might signal encephalitis and CNS metastatic mimicry should be considered in patients with a prior history of TBI and encephalomalacia.

Keywords: Autoimmune encephalitis; Cancer immunotherapy; Encephalomalacia; Immune related adverse events (irAEs); Metastatic brain tumor; Neuro-oncology; Traumatic brain injury.