Often I have heard people ask why if one drug is effective we shouldn’t simply take two or three at the same time? The answer is simple, because we don’t know if combining multiple drugs will make any difference to a man’s survival. The only way we can be sure is with good evidence. Good evidence requires, in the case of drugs, doing a clinical trial to see if a certain type of combination will be beneficial.
In such a late-stage clinical trial designed to see if Xtandi in addition to Zytiga along with a steroid worked any better than either of these drugs separately (combining them v sequencing them) in men with advanced prostate cancer whose disease had worsened it was concluded that the combination was not superior to the individual drugs.
This means that in the case of these two drugs combining them and using them at the same time was NOT better then either of the drugs by themselves.