Temporary Tumor Shrinkage Following Enfortumab Vedotin Therapy for Metastatic Urothelial Carcinoma After Radical Cystectomy With Neoadjuvant Chemotherapy: A Case Report.

A 39-year-old Japanese male patient presented with a chief complaint of gross hematuria persistent for two months. However, no relevant findings in the patient's medical and family history were observed. He was diagnosed with muscle-invasive bladder cancer, clinical stage T2bN0M0. After four courses of neoadjuvant chemotherapy with gemcitabine and cisplatin, the tumor size reduced by approximately 30%. The patient underwent robot-assisted radical cystectomy with standard lymph node dissection followed by intracorporeal ileal conduit reconstruction. Histologically, the tumor was diagnosed as a high-grade urothelial carcinoma invading the fatty tissue surrounding the bladder and metastasizing to the lymph nodes, with a pathological stage of ypT3aypN2M0. Four months after surgery, multiple metastases were detected, and treatment with pembrolizumab was initiated immediately. However, the patient did not respond to pembrolizumab. Therefore, a third-line treatment with enfortumab vedotin (EV) was initiated. Thereafter, the metastatic lesion shrank quickly, and the metastatic lesions almost disappeared after two courses of EV administration. Although new metastases were observed at other sites, there has been no regrowth to date. EV-related adverse events were not observed during follow-up. Eighteen months after the surgery, the patient remains alive with multiple metastases. Therefore, the sequence of treatment should be considered to maximize the therapeutic effect of EV, and, consequently, administering EV as early as possible may be important.