Hi @buzzliteyear, yes proton therapy is considered SBRT. Here's some info from Mayo Clinic https://www.mayoclinic.org/tests-procedures/sbrt/pyc-20446794#:~:text=Types%20of%20stereotactic%20body%20radiotherapy,that%20are%20near%20vital%20organs.

"Types of stereotactic body radiotherapy:
- Linear accelerator, also known as LINAC. LINAC machines use X-rays, also known as photons, to treat tumors.
- Proton beam, also called charged particle. This newer type of stereotactic radiotherapy uses protons to treat tumors over several sessions. Proton beam radiotherapy might be used to treat tumors in parts of the body that have already had radiation therapy. Or they can treat tumors that are near vital organs."

I'm tagging @jimcinak to make sure he sees your question about his experience with proton beam therapy with 5 treatments.

Buzzliteyear, did you opt for radiation?

First an apology for my very slow response. Lots of distractions and less focus.
I believe that my 5 proton beam treatments were pencil beam. (I’m not sure if there is a distinction between pencil beam and SBRT.) Short term I had some urethra irritation after treatment 2 and switched to taking flomax (which I still take). I think there may have been some minor irritation to my bowel.
My therapy also included a 4 month ADT shot. I really didn’t know of the need to work out during ADT to try to retain muscle mass. But, I went thru’ ADT in the middle of the pandemic, so there were other factors.
Long term: I just had my periodic blood draw sent to Mayo and my PSA remains less than .10 (essentially undetectable). So, even at five years I think of myself as “in remission” but not ‘cured’.
I hope that helps a little…