The clinical efficacy and limitations of dutasteride-regulated abiraterone metabolism in abiraterone-resistant patients: a prospective single-arm clinical trial in Chinese patients

BACKGROUND: The steroidal metabolism of abiraterone has been proposed to be involved in abiraterone resistance and limited approaches are available for abiraterone-resistant patients. Dutasteride regulates abiraterone metabolism in patients and might enhance the clinical efficacy of abiraterone. However, the function of dutasteride to overcome abiraterone resistance has not been investigated in clinic. Here we investigated the clinical efficacy and limitations of dutasteride in patients with abiraterone-resistant prostate cancer. METHODS: Abiraterone-resistant patients with metastatic castration-resistant prostate cancer (mCRPC) were enrolled in this single-arm, open-label study, patients were treated with dutasteride (0.5 mg/day), abiraterone (1,000 mg/day), and prednisone (5 mg twice daily), prostate-specific antigen (PSA) was tested monthly. The primary objective was PSA response, and the secondary objectives were to assess symptom relief and safety. Kaplan-Meier analysis was used to assess the PSA progression free survival (PSA-PFS) of patients. RESULTS: Twenty-two patients (median age: 75 years) were enrolled, and 19 patients completed the treatment. After a median treatment of 4.0 months, 7 (37%) patients showed a slight PSA reduction (−2% to −32%), and the median PSA-PFS was 2.0 months (1–7 months). No significant improvement was observed in Eastern Cooperative Oncology Group (ECOG) performance status. Bone pain was relieved in 6 patients after 1 month of treatment, but the improvement was not significant. No grade 3 or grade 4 adverse events were observed. CONCLUSIONS: The combination of dutasteride and abiraterone showed a mild effect in patients with abiraterone-resistant. The small sample size was the limitation of this study.