If it's the SPARTAN study, his oncologist got it backwards - 2/3 are getting the ARN 509 and only 1/3 gets the placebo. "The investigational medication will be given to 2 out of every 3 study participants." In addition, the number of one-month cycles of the drug depends on how well he reacts to it. So if he has no improvement while in the study, he is taken out of it. He continues on his normal Lupron injections throughout, so he doesn't have much to lose by being in it, even if he does get the placebo for a month.
However, that study excludes men with mets, and your signature says there was a met to the spine - will they let him on it anyway, or is it a different study?A Study of ARN-509 in Men With Non-Metastatic Castration-Resistant Prostate Cancer (SPARTAN)