Experience and Lessons Learned in the Treatment of Transforming Small Cell Neuroendocrine Carcinoma of the Prostate: A Case Report and Literature Review

Introduction

Small cell neuroendocrine carcinoma of the prostate (SCNECP) is a rare and highly malignant tumor that commonly transforms into conventional prostate adenocarcinoma (CPAC). Most of SCNECP cases cannot be detected and diagnosed early, and SCNECP is often diagnosed when there is liver and lung metastasis. Therefore, the early detection of the process from CPAC to SCNECP is crucial.

Case Report

We present a case of a 73-year-old man who was initially admitted to our hospital with metastatic CPAC. He was administered goserelin acetate 3.6 mg combined with bicalutamide tablets (50 mg) once daily for endocrine therapy and docetaxel (100 mg) combined with prednisone (5 mg) twice a day. After treatment, the prostate-specific antigen (PSA) level decreased significantly, but the CEA, CA199, and CA125 levels began to increase progressively after a short decline. However, no solid tumor recurrence was observed in multiple reexaminations. It was not until 9 months after the elevation of tumor markers that multiple metastatic lesions appeared in the liver, which finally confirmed the diagnosis of metastatic SCNECP. After chemotherapy with etoposide 360 mg combined with carboplatin 200 mg, the tumor size was significantly reduced, and tumor markers decreased. However, the remission time was only 3 months. The patient's liver metastases continued to grow, and CEA, CA199, and CA125 levels continued to increase.

Conclusion

During CPAC treatment, PSA levels continued to decrease, whereas CEA, CA199, and CA125 levels continued to increase. This suggests the possibility of the transformation of CPAC into SCNECP.

Successful Radiotherapy for Advanced Small Cell Carcinoma of the Prostate with Syndrome of Inappropriate Secretion of Antidiuretic Hormone

Small cell carcinoma of the prostate (SCCP) is rare in clinical practice. It is often accompanied with the syndrome of inappropriate antidiuretic hormone secretion (SIADH). We present a case of SCCP with SIADH that was successfully treated with radiotherapy in the metastatic lymphnodes and prostate. The patient was an 81-year-old male with a castrate-resistant prostate cancer (CRPC) with invaded rectum and multiple metastases of pelvic lymphnodes. Hyponatremia was present. After radiotherapy, serum sodium increased and neuron-specific enolase (NSE) decreased. To our knowledge, this is the first case of SCCP with SIADH treated with radiotherapy to improve hyponatremia.