Lack of testosterone, ADT, does suppress the PSA. It could be considered "falsely low" for that reason in a sense, but it's perfectly ok. You can certainly expect the PSA to pretty much remain undetectable during ADT. When that stops, and the testosterone recovers, the PSA may well go up a ways.
After radiation there is often a PSA "bounce" as it's called, but ADT masks that phenomenon. Once the ADT "releases", the PSA will likely rapidly head up to where it would have been without ADT. That trend can be quite alarming at first, but it will also likely level off and begin to descend as the radiation develops its longer term effectiveness. Radiation isn't an instant "cure" like surgery. It takes time to do its work.
I looked long and hard for studies about
PSA trends after radiation and ADT. There is very little published, and mostly the doctors just don't know what that pattern could or should be. They just don't know.
Everyone worries about
recurrence, but there are ASTRO guidelines
for that. The guidelines make sense to me. In fact, without the guidelines they use now, I might have been considered recurrent and embarked on some (unnecessary) life-altering treatments. However, per the guidelines we waited it out (looking for it to go over 2.0), and my PSA has now leveled out a bit over 0.5 and I'm quite pleased with that.
[Edit: added link]
Bx: 6/12 pos, G9=5+4 (80%, 60%), 4+5 (2@100%, 80%, 10%), PNI+
cT3a (3T mpMRI: Bilateral EPE, NVB+, SV-, LN-)
Date PSA fPSA
9/12 4.1 15%
3/13 5.2 12% PCA3=31
IGRT by IMRT, 44 done 8/28/13: 50.4 Gy pelvic nodes, 79.2 Gy prostate
ADT2 3 yrs: Lupron/Casodex, ended 3/16
PSA <0.1 : 8/13 - 5/16;
0.2-8/16, 0.5-12/16, 0.7-3/17, 0.8-5/17, 0.8-7/17, 0.7-10/17, 0.6-1/18
Post Edited (Redwing57) : 3/8/2018 7:11:53 AM (GMT-7)