Radiation-induced leiomyosarcoma of the prostate after brachytherapy for prostatic adenocarcinoma

Radiation therapy (RTx) has been employed as a curative therapy for prostatic adenocarcinoma. RTx-induced sarcomas (RISs) are rare, late adverse events, representing less than 0.2% of all irradiated patients. RISs are more aggressive tumors than prostatic adenocarcinomas. Herein, we present a case with RTx-induced prostatic leiomyosarcoma after permanent brachytherapy for prostatic adenocarcinoma. A 69-year-old male presented with dysuria and gross hematuria. Six years previously, he had been diagnosed with localized prostate cancer and was treated by permanent brachytherapy. Urethroscopy showed stenosis by a tumor at the prostate. Transurethral prostatectomy was performed for a diagnosis. Based on pathological findings, the diagnosis was leiomyosarcoma of the prostate. He was treated with three cycles of neoadjuvant chemotherapy (CTx) that consisted of doxorubicin and ifosfamide (AI), followed by a prostatocystectomy with intrapelvic lymphadenectomy. The tumor extended from the prostate and infiltrated the bladder wall and serosa with lymphatic and venous invasion. The surgical margin was negative, and no residual prostatic adenocarcinoma was observed. The proportion of necrotic tumor cells by neoadjuvant CTx was around 50%. Subsequently, adjuvant CTx was offered, but the patient chose a follow-up without CTx. Local recurrence and lung metastasis were detected by computed tomography 3 months after the surgery. He was treated again with AI. However, CTx was not effective and he died 6 months after the operation. In conclusion, an effective treatment strategy for prostatic sarcoma should be developed in the near future, although the clinical feature of prostatic sarcoma remains unclear due to its rare incidence.