I have not read all responses so I may duplicate comments.
1) I would ask for a decipher test to see how aggressive cancer is, maybe treatment is not required now.
2) I had Proton at 69, honestly I don’t think I would do it again. I believe I am cured and that’s number one but it is CT guided. It’s like using a highly accurate gun with a not so accurate scope. Some speculate that since you are positioned via fiducial. Then you have to wait until accelerator is ready giving time for additional movement.
3) After completion the doc tells me rectal bleeding happens in about 30% of cases.
4) I have a study regarding proton and how important spacers are, there appears less margin for error.
5) Talk to California Proton about bleeding.
6) Finally I think MRI guided SBRT is superior so why not go with it.

All my opinions