Abstract
INTRODUCTION: Pembrolizumab is the standard therapy for urothelial carcinoma treatment; however, adverse events have been noted. Here, we report a rare case of vision loss as an immune-related adverse event of pembrolizumab therapy in a patient with metastatic renal pelvic cancer. CASE PRESENTATION: A 69-year-old man treated with pembrolizumab for lung and lymph node metastases of renal pelvic cancer experienced significant vision loss in both eyes after 11 treatment cycles. Without magnetic resonance imaging confirmation owing to an MRI-unsafe pacemaker, his clinical features suggested immune checkpoint inhibitor-associated optic neuritis. Pembrolizumab was discontinued, and the patient received steroid pulse and immunoglobulin therapy. His vision in the right eye improved, but that in the left eye remained unchanged. He maintained a partial response for 36 months despite pembrolizumab discontinuation. CONCLUSION: Despite its rarity, vision loss is a potential irAE in patients treated with ICIs, including pembrolizumab.