Prolonged treatment with three-weekly docetaxel plus daily prednisolone for metastatic castration-resistant prostate cancer: A multicenter, phase II, open-label, non-comparative, extension study in Japan

Background: There are few reports of long-term treatment with docetaxel in castration-resistant prostate cancer (CRPC) because of the limit of a maximum of ten cycles of treatment in TAX327 showing a survival benefit. Therefore, this study, ARD6563, was conducted to evaluate the safety of more than ten cycles of docetaxel in metastatic CRPC. Methods: We enrolled patients who had received ten cycles of docetaxel in the preceding study, ARD6562. For ARD6563, patients received docetaxel every 3 weeks, at the last dose (70, 60, or 50 mg/m ²) received for cycle 10 in ARD6562, with prednisolone 5 mg orally twice daily. Results: The safety analysis set comprised 15 patients (median age, 64 years; performance status, 0 in 87%) out of 43 patients treated in ARD6562. The median initial dose of docetaxel was 60 mg/m², and the median number of additional cycles administered was 8 (range, 1-42). The relative dose intensity was 78.0% for docetaxel and 98.0% for prednisolone. Dose reduction was needed in 3 cycles because of grade 3 infection, febrile neutropenia, and grade 2 neuropathy. Administration delay was necessitated in 6 cycles because of grade 1-2 nonhematological toxicities. The major grade 3-4 toxicities were myelosuppression. Five patients who had an observed partial response or stable disease in ARD6562 maintained their clinical response in ARD6563. The study treatment was discontinued in 10 patients because of disease progression and in 4 patients for serious toxicities. There were no treatment-related deaths. Conclusions: Long-term docetaxel with prednisolone is feasible in selected Japanese patients with CRPC.