Prostate cancer in large prostates

Mine is 120 with a PSA of 2.9. Had a 30 core transperineal MRI fusion biopsy that found 5 cores all from the area where the MRI showed the Pirads 4 lesion that showed cancer. Most were 3-4 but 2 were 4-3 Gleason and I did have another pathologist look at the cores for a 2nd opinion. Mayo also had me do a PSMA Pet scan to see if it had spread and it was confined to the prostate. I wanted the SpaceOar gel and had that inserted when the markers were implanted. Chose the 5 session Proton radiation treatment at Mayo Phoenix. First session was a piece of cake and I drank my coffee on the way home no problem. Today was the 2nd session and I drank my mug on the way home and finished the pot when I got home. When they say to avoid coffee as it irritates the bladder they were not joking. I was peeing every 10 minutes all afternoon till it got out of my system after dinner tonight. 2 down and 3 more to go. I am 74 and walk over 10,000 steps every day and lift weights in my home gym.

What if the cancer has spread to areas where the cancer is very difficult to or just can't be surgically removed?