Testing Two Oral Drugs Combination (Cediranib and Olaparib) Compared to a Single Drug (Olaparib) for Men With Advanced Prostate Cancer

Inclusion Criteria: * Patients must have histologically confirmed progressive, metastatic castration resistant prostate adenocarcinoma by meeting ALL the following: * Pathology of prostate gland or metastatic disease must confirm the diagnosis of prostate adenocarcinoma; mixed histology with other variants including but not limited to small cell or neuroendocrine differentiation must be discussed with the study principal investigator (PI) * Metastasis must be documented by radiographic evidence * Castration resistance must be documented with surgical or medical castration with serum testosterone \< 50 ng/dL (\< 2.0 nM); if the patient is being treated with luteinizing hormone-releasing hormone (LHRH) agonists (patient who has not undergone orchiectomy), this therapy must have been initiated at least 4 weeks prior to cycle 1, day 1 and must be continued throughout the study * Progression must be evidenced and documented by any of the following parameters * Two consecutively rising PSA values, above the baseline, at a minimum of 1-week intervals; the minimal value to enter the study is 1.0 ng/ml or greater; the reference value (#1) is the last PSA measured before increases are documented, with subsequent values obtained a minimum of 1 week apart; if the PSA at time point 3 (value #3A) is greater than that at point 2, then eligibility has been met; if the PSA is not greater than point 2 (value #3B), but value #4 is, the patient is eligible assuming that other crit…