A number of doctors advise that a man should get as much benefit as he can from each treatment before he moves onto the next.
Zytiga (abiraterone) and Xtandi (enzalutamide), in particular should not be stopped just because PSA is rising again.
Treatment should continue until radiation shows things are getting worse, or clinical symptoms such as greater pain. The only time that PSA should be a signal for ending is if it goes up for more than 50 ng/mL above its lowest point while the drug is being used.
Becker studied whether this advice was being followed by ordinary doctors, not just those in the larger research hospitals in the big cities. In American veterans hospitals, he found the PSA level at the beginning of treatment most men of them matched the PSA at the end of treatment, showing that this group of men was not getting the full benefit of either of these drugs.
One of the studies which advise not to stop to early: