Hi Darren.
Like you, I was diagnosed as G9 with locally advanced PC. My presenting PSA was 18 up from <3 six months previously. Both my dad and elder brother died from the disease so I was considered at high risk. I was put on HT straight away and had six cycles of chemo soon after. Following that I had 37 fractions of RT. After the chemo and RT ended my PSA was down to <0.5, likewise my testosterone. A PET scan showed that my PC had shrunk considerably.
I am continuing on the HT (Zoladex) but most recently, while my testosterone has stayed minimal, my PSA has risen, doubling every few months which is concerning. The latest reading was 3.8. I am due for another PET scan this week to see if that reveals the cause of this rise. I will be seeing my oncologist a few weeks after that to learn the results.
So, from my experience, it would seem that PSA can rise following treatment. Right now I do not know the cause or implications of this. I will check back in with this thread once I know more.
Best wishes for a drop in your next PSA test.