Metastatic Urothelial Carcinoma With Sarcomatoid Subtype After Robot-Assisted Radical Cystectomy Successfully Treated With Pembrolizumab

A 76-year-old man who was diagnosed with urothelial carcinoma (UC) in the bladder diverticulum was referred to our institution. The patient was diagnosed with muscle-invasive bladder cancer, which was confirmed by magnetic resonance imaging that showed tumor invasion into the fatty tissue surrounding the diverticulum. After two cycles of neoadjuvant gemcitabine and cisplatin, he underwent robot-assisted radical cystectomy (RARC) with pelvic lymph node dissection followed by intracorporeal ileal conduit. The histopathologic diagnosis of the bladder tumor was UC with squamous differentiation and sarcomatoid subtype and ypT3bN0M0 without positive surgical margins. The patient refused any adjuvant therapy. Six months after RARC, the patient visited our institution with a complaint of suddenly occurring generalized pain. Because 18 F-fluorodeoxyglucose positron emission tomography-CT showed multiple metastases, including bone, para-aortic lymph nodes, and pleura, pembrolizumab was initiated as a second-line treatment. After two courses of pembrolizumab, the patient's symptoms remarkably improved, and the abnormal systemic accumulation on PET-CT almost disappeared. After 26 months of continuous treatment with pembrolizumab, the patient remains disease-free. Several studies have been reported that focused on tumor subtypes and programmed cell death ligand 1 (PD-L1)-positive tumor cells as candidate biomarkers in relation to the efficacy of pembrolizumab. The higher proportion of PD-L1-positive cells in the sarcomatoid subtype may have resulted in favorable oncological outcomes compared with pure UC.