I guess you are in the same boat as me, still a fairly low PSA but one which is consistently rising.
My own thoughts, and that is all they are, the uniformed thoughts of a layman, are as follows.
Those of us who have had RT as opposed to RP are still left with a residual 'healthy' prostate gland, which might be expected to make some PSA?
Over the years following RT, the healthy cells of our prostate gland should recover and grow, so some sort of increase in PSA is only to be expected?
Even if cancer has returned, either in the prostate or at some secondary location, the tumour can't be very big if it is only churning out such a low level of PSA. So presumably no point having scans etc as there is nothing big enough to see?
Choice is therefore whether to go back on HT or not?
Last time I did that, on the recommendation of my consultant's houseman, was when my PSA had gone from 2 to 4 to 6 in as many months. At my next consultation, the Consultant browsed my notes and said he might have not have put me on HT so soon, he may have been tempted to see how fast the PSA would rise.
As and when the time comes to go back on HT, I am inclined to opt for intermittent HT, and if that was the case the question is how high would we let PSA rise to during the intermittent periods off HT? There seems little point starting HT until PSA has reached that threshold?
I don't know if any of these thoughts help you, I am merely trying to rationalise my own dilemma.
All the best.