Pembrolizumab Treatment and Pathologic Therapeutic Evaluation for Granulocyte Colony-stimulating Factor-producing Bladder Cancer: A Case Report and Literature Review.

Granulocyte colony-stimulating factor (G-CSF)-producing bladder cancer is a rare variant subtype of bladder cancer with a poor prognosis. Pembrolizumab has improved overall survival in bladder cancer and is widely used as a standard second-line treatment. However, no reports on G-CSF-producing cancer treated by pembrolizumab are available. We report a case of the pathologically evaluated antitumor effect of pembrolizumab, a programmed death-1 immune checkpoint inhibitor antibody, in G-CSF-producing bladder cancer. A 53-year-old male patient underwent 4 courses chemotherapy with a combination of gemcitabine and carboplatin before a radical cystectomy with ileal neobladder. Four months after the surgery, local recurrence was detected in the pelvis and therefore pembrolizumab was used. One week after its administration, the patient showed increased mucus in his urine. A computed tomography scan and cystoscopy revealed a fistula between the ileum and the neobladder. He subsequently underwent partial ileectomy and repair of the neobladder-ileum fistula. Pathology-diagnosed tumor response to pembrolizumab in the metastatic tumor showed predominant infiltration by lymphocytes, unlike that in the primary bladder cancer. The patient has shown complete response and no recurrence at 1 year after the beginning of treatment, and therapy is still continuing. Although many questions still remain regarding the treatment of G-CSF-producing bladder cancer, pathologic evaluation of the present case suggests that treatment with pembrolizumab may be one option for G-CSF-producing bladder cancer that has failed chemotherapy treatment, similar to non-G-CSF-producing bladder cancer.