Go to a radiation oncologist, not a urologist, and do it quickly! It's kind of crazy that your urologist did not refer you sooner, especially with a tertiary 5 and EPE. Yes, you're right that he will probably recommend ADT +SRT. There are experimental uses of shortened radiation schedules, proton, and SBRT, but those are limited to clinical trials. The standard of care is 7 weeks of IMRT to the prostate bed.
You should have a pelvic CT scan to see if any lymph nodes are enlarged.
In SW Florida, I'd recommend Constantine Mantz in Ft. Myers.
Allen - not an MD
•PSA=7.3, prostate volume=55cc, 8/17 cores G6 5-35% involvement
•SBRT 9 yr onc. results
•SBRT 7 yr QOL results
•treated 10/2010 at age 57 at UCLA,PSA now: 0.1,no lasting urinary, rectal or sexual SEsmy PC blog