Comparative Study of Alternative Antiandrogen (AA) Therapy and Early Initiating of Enzalutamide for Castration-resistant Prostate Cancer (CRPC) After Combined Androgen Blockade (CAB) Therapy.

Multicenter, Prospective, Randomised and Comparative Study of AA Therapy and Early Administrating Enzalutamide in Participants With CRPC Previously Treated With CAB Therapy Using Bicalutamide.

The objective of this study is to compare the efficacy and safety of enzalutamide or alternative AA therapy in CRPC participants who were previously treated with a combined androgen blockade therapy which included bicalutamide (Bic-CAB). Efficacy and safety of enzalutamide and alternative AA therapy will be evaluated, and effective therapy against CRPC after treatment with Bic-CAB will be investigated.

Inclusion Criteria:

• Testosterone of less than 50 ng/dL
• Participants who was detected of disease progression on image or relapse of PSA (All PSA values measured 3 time at least one week interval are consecutively increased and final value is 2 ng/mL or more. If third value is not higher than second one, fourth measurement will be undertaken and its value must be higher than second one.)
• Participants who relapsed after CAB with bicalutamide
• Eastern Cooperative Oncology Group (ECOG) performance status is 0 or 1
• Aged 20 years or older
• Participants who provided written informed consent

Exclusion Criteria:

• Any prior treatment with enzalutamide, flutamide, abiraterone or chemotherapy, except for neoadjuvant therapy
• With active double cancer
• Any prior treatment with bicalutamide within 6 weeks
• Participants who received systemic biological therapy (except for existing approved drug for bone or treatment with luteinizing hormone-releasing hormone (LHRH) analogue) or received treatment with other antitumor agent for prostate cancer
• With serious complication
• History of hypersensitivity to enzalutamide or any other excipient of enzalutamide
• History of hypersensitivity to flutamide-containing agent
• With liver dysfunction
• Participants who are considered as inadequate by the investigator