My situation is not exactly what you asked about, but it’s close enough that I thought I would respond. I had RP 2 years ago at age 59. My PSA was 23, Gleason 4+4=8, stage 3 with seminal vesicle involvement. 60 days post RP, my PSA declined to 7. I started intermittent Bicalutamide in dosages between 50-150 milligrams per day. Got my PSA down to 0.23 in 6 months. Then stopped for 2-3 months until PSA rose above 2.0. Now I will be on the bicalutamide for 2-3 months then off for 2-3 months depending on how quickly the PSA rises and falls. I am being treated by a Dr in Mexico City. I go once a year for a PET/PSMA scan and I have two tumors in the prostate bed but no metastasis. My Mexican Dr says I can go on indefinitely like this, but I’m going to see an RO at Miami Cancer Institute in December who uses the MRIdian equipment to see if a cure is still possible. If the RO thinks there is a decent chance, I will go for it. I think the intermittent ADT is better for quality of life than constant ADT, but it’s still bad enough that if there is a reasonable chance of getting off it through RT, I will try it.

Greetings;
My take would to have a short course of ADT first then have the radiation because the ADT weakens the cancer then the radiation finishes it off easily.
I don't totally agree with the doctor's opinion that you can go on ADT indefinitely because of the side effects.
Given that after RP the psa only dropped to 7 means that it is still out there and after the ADT it went from .23 to 2 in 2-3 months means that you have to get on it ASAP.
I researched the MRIdian and it is impressive.
Please keep us in the loop.
Best wishes

Dr. Scholoz on Utube has many helpful videos on your situation. He would advise to get on Lupron since the cancer is in the bed of where the prostate was. I have a friend who got his removed 7 years ago and he had a similar Gleason 7 and PSA around 7 like me. He gets blood work done and if it bumps up from .1, he get a Lupron and he gets one about once a year. A 3 month one, I had no cancer per CT and Bone S. I had it removed 2.4 months ago. I go back on Nov. 16 for my first blood work. If the PSA is above 0, I get a PMSA Pet Scan and that identifies any spots. If a spot is detected where the prostate was, I get on Lupron. If a spot is outside of where the prostate was, I have the spot pinpointed and then targeted Beam Radiaition will poison the little bastard. I am 70 just now. I do the Kelgel and Pelvic exercises and now am working out hard again and doing Core exercises, 1,000 Crunches a day. I am on some pill for pee control but I swear to all of you, I pee 200 a day. I put up with it because I am so happy to be alive.