Immunotherapy-related cystitis induced by nivolumab: A case report and review of the literature.

Immune checkpoint inhibitors (ICIs) like nivolumab have revolutionized cancer treatment but can cause immune-related adverse events (irAEs), including rare cystitis. This case report describes a gastric cancer patient who developed urinary symptoms, such as hematuria and frequent urination, after nivolumab treatment. Despite initial antibiotics, symptoms worsened, leading to a diagnosis of immune-related cystitis. Intravenous methylprednisolone provided rapid relief and restored renal function. Early recognition and corticosteroid treatment are crucial for managing ICI-induced cystitis and preventing unnecessary antibiotics.