(Edited, to add info) To answer the original question, --I am not one that had Proton Beam SBRT. I did go to the Mayo PHX during Sept-Dec 2019. My oncologist first suggested the PB SBRT. but as Colleen stated, it is new enough that it is still only available at a few centers (but, expensive, including even the cost of having built any center for it.), and despite several efforts by some, my insurance would not cover it at the time. So, we went with the IMRT, and hsd 38 sessions. (I am aged 67, as well. My PC was contained within the prostate, and the IMRT had multiple modulations to it, in order to avoid the nearby organs. I also had the SpaceOar put in there, prior to the radiation treatments, to protect the rectum.)
There was also the offer of the 5 visit type, but in researching it, I just felt better about having more sessions, rather thsn fewer. We had a friend's home to rent for a fair price, and so we were able to stay in the area. I had plenty of Sick Leave time w/work, and used FMLA. I was very satisfied with my oncologist there, the entire cancer center workers, and my prognosis.
Many in our family have been patients at both Mayos in Rochester and Phoenix, for a multitude of issues. We love that records can be viewed by all the depts, as needed, even in different locations, and that once you are a patient there, all depts are available to you, and there are not Multiple charges for "new patient fees" every time you have to be seen at a different dept. They ALL work as a Team. We highly recommend the Mayo.