Conversion to Pathological Complete Response by Enfortumab Vedotin in Metastatic Sarcomatoid Urothelial Carcinoma With Nectin‐4 Expression: A Case Report

Introduction Sarcomatoid urothelial carcinoma (UC) is an extremely rare and aggressive subtype with a poor prognosis. Reports on the efficacy of enfortumab vedotin (EV) in this subtype remain limited. Case Presentation A 74‐year‐old man presented with gross hematuria and was diagnosed with metastatic sarcomatoid UC of the urinary bladder with Nectin‐4 expression. First‐line chemotherapy with gemcitabine plus carboplatin therapy was initiated; however, lymph node metastases progressed. After second‐line pembrolizumab therapy, new pulmonary and para‐aortic lymph node metastases developed. Third‐line EV therapy achieved a partial response in the bladder cancer and complete response in metastatic lesions. The patient subsequently underwent robot‐assisted radical cystectomy with ileal conduit diversion, and pathological examination revealed no residual carcinoma (ypT0N0). He has remained disease‐free for 30 months without additional therapy. Conclusion EV may induce substantial and clinically meaningful responses in selected patients with metastatic sarcomatoid UC expressing Nectin‐4, even after failure of platinum‐based chemotherapy and immune checkpoint inhibition.