Definitely a doctor question. Depends on many things. Gleason score, type of cancer, stage of cancer, etc. My initial PSA as 80+ when discovered. So its matastisized. Levels said too late for surgery-but took my doctors advice and went for surgery and it was effective. Then had a level of under 1.0-then had the chemo and CAB sessions.
Now under .008. So do not think there is a hard line rule-but must consider all aspects of the person affected. I recommend you let your care provider advise you on this one.