The primary goal is to prospectively estimate the median radiographic PFS of African American and Caucasian men with mCRPC to abiraterone acetate and prednisone.

This is a non-comparative pilot open-label, parallel arm, multicenter study of abiraterone acetate in African American and Caucasian men with mCRPC. Patients will self-report on race and 50 patients will be enrolled into each group. Patients will be treated on open-label treatment until evidence of disease progression as defined by Prostate Cancer Working Group Two (PCWG2) definition or until two years at which point they will roll over to the standard of care at that time. The study agent abiraterone acetate will be administered by the patient at a dose of 1000mg orally once daily with prednisone 5 mg BID in 4-week cycles throughout the treatment period.

Inclusion Criteria:

• Male, age ≥ 18 years

• Karnofsky performance status ≥ 70

• Life expectancy of ≥ 12 months

• Willing to take abiraterone acetate on an empty stomach; no food should be consumed at least two hours before and for at least one hour after the dose of abiraterone acetate is taken, and should be able to swallow tablets whole, without crushing/chewing tablets

• Patients who have partners of childbearing potential must be willing to use a method of birth control with adequate barrier protection as determined to be acceptable by the principal investigator and sponsor during the study and for 1 week after last dose of abiraterone acetate

• Adequate laboratory parameters

• Histologically confirmed diagnosis of adenocarcinoma of the prostate. Histologic variants of prostate cancer, including neuroendocrine features and small cell carcinoma of the prostate are excluded

• Radiographic evidence of metastatic disease; evaluable non-target lesions and/or bone only metastasis are permitted

• Ongoing ADT using an LHRH agonist (e.g. leuprolide, goserelin) or antagonist (e.g. degarelix) must continue on therapy unless prior bilateral orchiectomy has been performed. Screening serum testosterone must be <50 ng/dl

• PSA ≥ 2.0 ng/mL

• Evidence of of castration resistant disease on ADT as evidenced by one of the following:

  • Absolute rise in PSA of 2.0 ng/mL or greater, minimum 2 consecutive rising PSA levels with an interval of ≥ 1 week between each PSA level, OR
  • 2 consecutive PSA levels 50% or greater above the PSA nadir achieved on ADT and separated at least 1 week apart, OR
  • CT or MRI based evidence of disease progression (soft tissue, nodal or visceral disease progression) according to modified PCWG2 criteria or modified RECIST 1.1 criteria, or at least 1 new bone scan lesion as compared to the most immediate prior radiologic studies)

• A minimum of 2 weeks elapsed off of antiandrogen therapy prior to start of study drug (i.e. flutamide, nilutamide, bicalutamide)

• A minimum of 4 weeks elapsed off of sipuleucel-T prior to start of study drug

• A minimum of 4 weeks from any major surgery prior to start of study drug

• Self-reported race of either African American or Caucasian

• Ability to swallow, retain, and absorb oral medication

Exclusion Criteria:

• Prior treatment with abiraterone acetate or enzalutamide
• Active infection or other medical condition that would make prednisone/prednisolone (corticosteroid) use contraindicated
• Any chronic medical condition requiring a higher dose of corticosteroid than 5mg prednisone/prednisolone bid
• Have known allergies, hypersensitivity, or intolerance to abiraterone acetate or prednisone or their excipients
• Pathological finding consistent with small cell carcinoma of the prostate
• Symptomatic Liver or visceral organ metastasis
• Have a history of gastrointestinal disorders (medical disorders or extensive surgery) that may interfere with the absorption of the study agents
• Known brain metastasis
• Prior cytotoxic chemotherapy or biologic therapy for the treatment of CRPC
• Previously treated with ketoconazole for prostate cancer for greater than 7 days
• Prior systemic treatment with an azole drug (e.g. fluconazole, itraconazole) within 4 weeks of Cycle 1, Day 1
• Uncontrolled hypertension (systolic BP ≥ 160 mmHg or diastolic BP ≥ 95 mmHg). Patients with a history of hypertension are allowed provided blood pressure is controlled by anti-hypertensive treatment.
• Poorly controlled diabetes
• Active or symptomatic viral hepatitis or chronic liver disease
• History of pituitary or adrenal dysfunction
• Clinically significant heart disease as evidenced by myocardial infarction, or arterial thrombotic events in the past 6 months, severe or unstable angina, or New York Heart Association (NYHA) Class II-IV heart disease or cardiac ejection fraction measurement of < 50% at baseline
• Atrial Fibrillation or other cardiac arrhythmia requiring therapy
• Other malignancy, except non-melanoma skin cancer, with a ≥ 30% probability of recurrence within 24 months
• Administration of an investigational therapeutic within 30 days of Cycle 1, Day 1
• Any condition which, in the opinion of the investigator, would preclude participation in this trial