Lots to unpack there, bro! Well, the radiation will definitely play bladder games. I found that my sense of urgency is greater - when I gotta go, I gotta go NOW! But even that is better….
I did try a pump and hated it. It made my unit swell but the base remained shriveled cause I never took the 5 mgs Cialis daily after surgery.
Others will have more input than me but I would go straight to the Trimix injection and not waste time on penile rehabilitation at age 78….rehab for what?
You should ask your Lupron doc if you can use Trimix while on ADT or if you should wait. My sense is that you can but I cannot say for sure. Best
Phil

There are psychological approaches to dealing with an overactive bladder, but there's also a pill (Myrbetriq) that can relax the detrusor muscle and cut down on the nighttime bathroom trips significantly. It's a low-/no-side-effect medication, and doesn't conflict with our standard PCa meds, so it might be worth discussing with your care team (at least as a short-term helper).

What happens with radiation is that it sometimes fans out a bit from the prostate into the bottom of your bladder (it keeps spreading for a few weeks after the end of treatment, according to my RO). That's both good (it might catch any stray cancer cells that have made it just outside the prostate) and bad (it can cause mild irritation). Unfortunately, your parasympathetic nervous system misreads that mild irritation as a full bladder, and sends a "LET'S GO NOW!!" signal to your detrusor muscle, which contracts involuntarily and squeezes the bladder, so you're essentially fighting yourself: you're trying to hold the urine in with your sphincters and pelvic floor muscles while you're involuntarily trying to push it out with the detrusor muscle.