Post RARP I was told the ISD and dilatations could be affecting my PSA, but I think it was wishful thinking on the part of my team. My PSA only rose from 0.03 to .27 in two years of ISD. Post RT my PSA dropped from 0.27 to 0.04 and I was still performing ISD up until a few weeks ago.
You presumably still have some of your prostate left whereas mine was removed so not exactly the same situation.
Hope all goes well and you get it sorted.