Prostate brachytherapy followed by secondary urethral adenocarcinoma: A case report

Prostate brachytherapy carries a risk of secondary malignancies, with data regarding secondary urethral malignancies being particularly sparse. We report a case of secondary urethral adenocarcinoma presenting 14 years after low-dose-rate (LDR) brachytherapy. A 57-year-old man developed recurrent urethral stenosis after LDR brachytherapy for prostate cancer (2009). In 2023, subsequent resections confirmed HER2-positive, ERBB2-amplified urethral adenocarcinoma. After neoadjuvant oxaliplatin/capecitabine (CAPOX) therapy, he underwent cystoprostatectomy, urethrectomy, and ileal conduit. Pathology showed stage IIIB disease with negative margins. This case underscores a rare but severe complication of prostate brachytherapy, contributing to the clinical understanding of secondary urethral malignancies.