Immune Checkpoint Inhibitor-Induced Ureteritis and Cystitis in Patients With Lung Cancer and Uterine Malignancies: A Case Series and Literature Review.

Immune checkpoint inhibitors (ICIs) have demonstrated significant efficacy across various cancers but can cause immune-related adverse events (irAEs). While common irAEs such as dermatitis, pneumonitis, and colitis are well-documented, rare events like cystitis and ureteritis remain underrecognized. We report 3 cases of ICI-induced cystitis and ureteritis. The first case involves a 67-year-old female with lung cancer who developed immune-related cystitis and ureteritis after 3 cycles of pembrolizumab, with recurrence 8 months after discontinuation. Both episodes presented with hematuria, urinary frequency, and dysuria, and were responsive to corticosteroid treatment. The second case involves a 37-year-old female with cervical cancer who developed a truncal rash, hematuria, urinary frequency, and dysuria after the first cycle of cadonilimab, a PD-1/CTLA-4 bispecific antibody. Her condition worsened with rising serum creatinine levels. Imaging revealed bladder wall thickening and ureteral dilation. Partial symptom relief followed oral corticosteroids, but complete resolution was achieved with intravesical corticosteroid irrigation. The third case describes a 35-year-old female with endometrial cancer who presented with similar urinary symptoms and flank pain after 4 cycles of pembrolizumab. Rapid creatinine elevation necessitated ureteral stent placement, which failed to alleviate symptoms. After exclusion of infectious etiologies, immune-related cystitis/ureteritis was diagnosed. Symptoms resolved with intravenous corticosteroids. This report underscores the importance of early recognition and management of rare urinary irAEs to avoid unnecessary interventions and prolonged interruption of anti-tumor therapy. It also highlights intravesical methylprednisolone as a potential treatment modality that warrants further investigation.