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.