Successful Resection of Cisplatin-Resistant Renal Pelvic Cancer after the Administration of Pembrolizumab as Second-Line Therapy

: Pembrolizumab has been used as a second-line systemic therapy for urothelial carcinoma. We herein report a case of cisplatin-resistant renal-pelvic urothelial carcinoma that was successfully resected after pembrolizumab treatment. A 74-year-old woman was referred to our hospital for further examination for gross hematuria and a renal-pelvis tumor. Retrograde pyelography showed a defect lesion in her renal pelvis and urinary cytology of the renal pelvis showed class V. Because staging CT could not deny lung metastasis, we planned to perform nephro-ureterectomy after evaluating the response to neoadjuvant chemotherapy. After three courses of gemcitabine and cisplatin chemotherapy, the original site showed progression; thus, nephro-ureterectomy was cancelled. We introduced pembrolizumab as a second-line therapy. After four courses of pembrolizumab treatment, the size of the original lesion was significantly decreased. During these therapies the lung tumor size was unchanged; thus, we determined that the lung tumor was not metastatic and performed nephro-ureterectomy. A pathological examination demonstrated that the tumor was completely resected with a negative surgical margin. We described the first case in which cisplatin-resistant renal pelvic tumor was successfully resected after pembrolizumab treatment.