Acute Cerebellitis Due to Administration of Durvalumab for Recurrent Endometrial Cancer: A Case Report.

Immunotherapy with immune checkpoint inhibitors (ICI) has recently been introduced to advanced and recurrent endometrial cancers. The addition of durvalumab to standard carboplatin-paclitaxel (TC) therapy improved outcomes for patients with endometrial cancer. However, immune-related adverse events (irAEs) are being increasingly recognized, and neurological irAEs are rare, particularly those confined to the cerebellum. We present the case of a 55-year-old woman with recurrent endometrial cancer who developed acute neurological symptoms during treatment with TC plus durvalumab therapy. The patient presented with an unsteady gait, and initial brain magnetic resonance imaging excluded cerebral infarction. As her symptoms persisted, the patient was transferred to a tertiary neurology hospital. Neurological examinations revealed truncal ataxia, dizziness, dysarthria, and nystagmus. Based on neurological findings, cerebrospinal fluid and blood analyses, and the clinical course, the patient was diagnosed with immune-related cerebellitis. Chemotherapy was discontinued as the event was graded as a severe (grade 3) irAE. High-dose corticosteroid pulse therapy was administered twice, followed by intravenous immunoglobulin (IVIG), owing to an incomplete response. Despite treatment, nystagmus persisted. Although no disease progression was observed, her quality of life (QOL) was profoundly impaired, and supportive care was initiated. Neurological irAEs can cause irreversible sequelae and significantly impair QOL. When neurological symptoms are observed during ICI therapy, prompt collaboration with a neurologist and early intervention are essential to minimize long-term disability. This case highlights the importance of vigilance for rare neurological irAEs, such as immune-related cerebellitis in gynecological oncology practice.