A Study of Apalutamide (ARN-509) in Men With Non-Metastatic Castration-Resistant Prostate Cancer

This Phase 3 clinical trial is an essential step in the evaluation of an investigational medication to see if it may be useful in treating prostate cancer. The purpose of the SPARTAN study is to compare the safety and effectiveness of the investigational medication to placebo in delaying prostate cancer from spreading to other parts of the body. A placebo is a pill that looks like the investigational medication but does not contain any active medication, a dummy pill. Phase 3 studies are performed after preliminary evidence suggesting effectiveness of the drug has been obtained in previous Phase 2 studies. These studies are intended to gather the additional information about effectiveness and safety that is needed to evaluate the overall benefit-risk relationship of the drug. Study participants will take the oral investigational medication daily. One cycle of study treatment lasts 4 weeks or 28 days. The number of cycles will depend on how you and your cancer respond to the study medication. In order for the researchers to evaluate and compare the study results, there are two different study groups. Study participants will be randomly (like flipping a coin) assigned to one of these groups: * One group will receive their current treatment along with the investigational medication * One group will receive their current medications along with a placebo The investigational medication will be given to 2 out of every 3 study participants. Neither you nor the study staff will know which group you are in. However, in case of a medical emergency, your study doctor can quickly find out which treatment group you are in. All participants will continue to receive their current treatment along with either the investigational medication or a placebo. The selections will be random, and you may remain on investigational treatment until your disease worsens, or until significant side effects occur or you can no longer tolerate treatment.