Supplementary Material for: Giant cell temporal arteritis followed by severe encephalopathy induced by immunotherapy in a patient with metastatic renal cell carcinoma achieving durable partial response: A case report

Introduction: Combined immune-oncology (IO) regimens are the cornerstone of the current front-line systemic therapy for metastatic renal cell carcinoma (mRCC). Despite the fact that combined IO regimens show high efficacy, they are often accompanied with a wide spectrum of immune-related adverse effects (irAEs). Case Presentation: We describe a case of rare irAEs manifested as giant cell temporal arteritis (GCA) followed by severe encephalopathy occurring after continuing immunotherapy in a 66-year-old man with mRCC receiving combination of ipilimumab and nivolumab in the first line of systemic therapy. GCA occurred four months after the initiation of IO and responded promptly to the low-dose prednisone therapy. Four months after continuation of nivolumab maintenance, the patient was hospitalized due to severe irAE encephalopathy which presented as psycho-behavioral abnormalities and progressive cognitive decline. He was treated with high-dose methylprednisolone which led to complete resolution of the symptoms and IO was permanently discontinued. The patient achieved a durable partial response. Conclusion: Both GCA and the subsequent encephalopathy in our patient responded well to the corticosteroid therapy, leading to the complete resolution of the symptoms and the patient achieved durable partial response. Although, the risk of severe neurologic irAEs affecting central nervous system induced by IO re-administration, following previous discontinuation due to irAE, is not well-defined because of their rarity, this case highlights the need for caution, particularly in cases with a history of previous irAE-associated GCA.