Radiation‐Associated Enteric‐Type Urethral Adenocarcinoma 20 Years After Prostate Brachytherapy: A Case Treated With Neoadjuvant Gemcitabine‐Cisplatin and Robot‐Assisted Radical Cystectomy

Introduction Brachytherapy is a widely accepted treatment for prostate cancer, in which subsequent radiation‐associated enteric‐type urethral adenocarcinoma is extremely rare. Case Presentation An 83‐year‐old man with a history of cholecystitis, appendicitis, and hyperlipidemia who had undergone brachytherapy 20 years earlier presented with dysuria. Transurethral resection of the prostate revealed enteric‐type urethral adenocarcinoma. Imaging showed a space‐occupying lesion extending from the prostatic to the membranous urethra without distant metastasis. The patient received three cycles of gemcitabine and cisplatin as neoadjuvant chemotherapy, followed by robot‐assisted radical cystectomy after confirmation of tumor shrinkage. At 18 months postoperatively, he remained alive with no evidence of recurrence. Conclusion This case illustrates a rare secondary enteric‐type urethral adenocarcinoma after brachytherapy and highlights a potential therapeutic strategy for its management.