The purpose of this study is to characterize the tolerability profiles of enzalutamide and abiraterone acetate (with prednisone) -with specific focus on central nervous system (CNS) tolerability-and quality of life (QoL) after approximately 2 months of participants starting treatment with one of these agents for metastatic castration-resistant prostate cancer (mCRPC).

This is a multicenter (more than one study site), open-label (all people know the identity of the intervention), prospective, observational study to characterize the tolerability profile of treatment and quality of life (QoL) in participants receiving enzalutamide or abiraterone acetate (with prednisone) in a clinical practice setting. Approximately 100 male participants will be enrolled into this study, 50 participants will be recruited to each treatment arm. Participants will complete 2 scheduled on-site visits (Baseline and Month 2). Participants will primarily be observed for tolerability profiles of enzalutamide and abiraterone acetate (with prednisone) and safety over an observational period of 2 months.

Inclusion Criteria:

• Male 18 years of age or older
• Have confirmed metastatic adenocarcinoma of the prostate
• Are starting treatment with enzalutamide or abiraterone acetate (with prednisone) for metastatic castration-resistant prostate cancer (mCRPC) at the full recommended dose per each drug's respective prescribing information (PI)
• Have an Eastern Cooperative Oncology Group Performance Status score of 0 or 1
• Sign written informed consent

Exclusion Criteria:

• Have a pre-existing central nervous system (CNS) condition (including, but not limited to, history of stroke or dementia) that, in the participating physician's judgment, would preclude participation in the study
• Have known mental illness including, but not limited to, major depressive disorder, general anxiety disorder, or bipolar disorder that, in the participating physician's opinion, could significantly confound the patient-reported outcome (PRO) assessments
• Have a history of or ongoing seizure disorder
• Have severe hepatic impairment (Child-Pugh Class C)
• Have an active infection (example, human immunodeficiency virus [HIV], viral hepatitis) or other medical condition that would contraindicate the use of prednisone/prednisolone (systemic glucocorticoid)
• Have known alcohol or other substance abuse disorder
• Are routinely taking medication-including, but not limited to, over-the-counter medications, supplements, medical marijuana or prescription pain medication-that is known to cause mental confusion or sedation or are using any of the medications
• Are routinely taking systemic glucocorticoids (example, prednisone, prednisolone, dexamethasone) at a dosage higher than the equivalent of prednisone 10 milligram (mg) daily
• Are currently using or have previously used chemotherapy for any cancer including mCRPC
• Are concurrently using any first-generation androgen-receptor blocker (example, bicalutamide, flutamide, nilutamide) for mCRPC
• Have previously taken enzalutamide or abiraterone acetate with prednisone
• Are not capable of completing tests using a computerized system or completing a participant survey

Participants who have a confirmed metastatic adenocarcinoma of the prostate will receive either enzalutamide or abiraterone acetate with prednisone for the treatment at the discretion of their treatment physician and in accordance with clinical practice.