Seems to depend on whether you get to PSA < 0.1 and how long it takes you get there. The best is within 6 months. It means that 99%, possibly more of the cancer cell is 'suppressed'. If it takes longer, you are still ok but it might indicate some of the cancers are a little harder to suppress. Suppressed means either killed or hybernates. Mostly killed. Above PSA 0.2 you got work to do. If under that, you are still ok.
Johns defines desease free as PSA 0.5. That is the cut off these studies use.