Urethral Metastasis of Therapy‐Induced Neuroendocrine Prostate Cancer Successfully Managed With Chemoradiotherapy: A Case Report

Introduction Urethral metastasis of prostate cancer is exceptionally rare, particularly in castration‐resistant disease. Therapy‐induced neuroendocrine prostate cancer (t‐NEPC) is an aggressive variant with limited treatment options. Case Presentation A 72‐year‐old man, 14 years after diagnosis of prostate adenocarcinoma treated with androgen deprivation therapy, presented with hematuria and dysuria. Prostate‐specific antigen was 2.05 ng/mL and neuron‐specific enolase was 28.0 ng/mL. Urethroscopy revealed papillary tumors in the pendulous urethra. Histology showed high‐grade adenocarcinoma with a small cell carcinoma component, positive for synaptophysin and prostate‐specific antigen. Genomic profiling demonstrated PTEN loss, TP53 mutation, and androgen receptor amplification. Platinum‐based chemotherapy with external‐beam radiotherapy achieved durable urethral local control despite later distant progression; the patient survived 2 years 10 months. Conclusion Platinum‐based chemoradiotherapy may provide durable local control of urethral metastasis from t‐NEPC.