Favorable response to pembrolizumab in granulocyte colony‐stimulating factor‐producing upper urinary tract urothelial carcinoma

INTRODUCTION: Granulocyte colony‐stimulating factor‐producing upper urinary tract urothelial carcinoma is rare, with a poor prognosis. Advanced urothelial carcinoma is currently treated with immune checkpoint inhibitors, whose efficacy for granulocyte colony‐stimulating factor‐producing upper urinary tract urothelial carcinoma remains unclear. CASE PRESENTATION: A 66‐year‐old male diagnosed with clinical stage T3N1M0 urothelial carcinoma of the right ureter with giant hydronephrosis underwent right radical nephroureterectomy. Local recurrence, leukocytosis, and elevated serum granulocyte colony‐stimulating factor levels were observed approximately 3 months after surgery. Chemotherapy was started but failed to control the disease. Therefore, pembrolizumab was chosen as the second‐line treatment. After this treatment, the blood leukocyte count rapidly normalized, and a clinically favorable response was achieved. There was no recurrence 10 months after the beginning of pembrolizumab treatment, which is still ongoing. CONCLUSION: Pembrolizumab may be a treatment option for advanced granulocyte colony‐stimulating factor‐producing upper urinary tract urothelial carcinoma.