Undifferentiated Castration-Resistant Prostate Cancer Successfully Treated With Carboplatin and Paclitaxel

Castration-resistant prostate cancer (CRPC) is a heterogeneous and aggressive disease with limited treatment options, particularly in poorly differentiated cases that lack androgen receptor expression and progress rapidly even under conventional therapies. Here, we present a rare case of poorly differentiated CRPC that exhibited a remarkable response to carboplatin and paclitaxel therapy.

A 53-year-old man with metastatic, castration-sensitive prostate cancer (cT3bN1M1b, PSA 9.39 ng/mL, Gleason 4 + 5) underwent androgen deprivation therapy using bicalutamide and leuprorelin. Nine months later, he developed CRPC, despite undetectable PSA levels. A supraclavicular lymph node biopsy revealed a poorly differentiated carcinoma. Immunohistochemistry was negative for PSA and NKX3.1 and positive for CK5/6. These results excluded neuroendocrine carcinoma and supported a diagnosis of undifferentiated carcinoma. Systemic chemotherapy with carboplatin (area under the curve, five) and paclitaxel (200 mg/m²) was initiated. Partial remission was achieved at 2 months, and complete remission was confirmed at 18 months. After 73 cycles, chemotherapy was discontinued, and the patient has remained in remission during follow-up.

This case highlights the potential efficacy of carboplatin and paclitaxel in treating poorly differentiated CRPC, suggesting the need for further investigation into platinum-based regimens for aggressive prostate cancer variants.