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

This randomized phase II trial studies how well olaparib with or without cediranib works in treating patients with castration-resistant prostate cancer that has spread to other places in the body (metastatic). PARPs are proteins that help repair DNA mutations. PARP inhibitors, such as olaparib, can keep PARP from working, so tumor cells can\'t repair themselves, and they may stop growing. Cediranib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Giving olaparib and cediranib may help treat patients with castration-resistant prostate cancer.