@brianjarvis
As you know there are many types of cancer than prostate. Almost every medical institution that I am familiar with these days will refer those with cancer that are children, have eye cancer, brain cancer, etc. to proton facilities. This include Mayo Jacksonville which does not have proton radiation just photon. Mayo Jacksonville is building a new cancer center which will have proton radiation.

I don't think Mayo and all the research they do would spend the hundreds of millions of dollars to build a new cancer center with proton radiation if proton was not beneficial addition to treating cancer.

Not one of my medical providers told me anything different than this. There is no difference in success rate of radiation treatments from proton and photon. They both have the same success rates. The main difference is photon comes in, hits target, can continues out through body. Proton enters a low dose, releases it's full dose strength at progammed target, and stops.
The below was copied directly from American Cancer Society.
Particle beam radiation therapy. A common type of particle beam radiation therapy is proton therapy. Proton therapy focuses beams of protons on the cancer.

The beams used in proton therapy only travel a certain distance. The radiation beam stops at the tumor and doesn’t go beyond it, so the tissues behind the tumor are exposed to very little radiation.

This is different than the photons (x-rays) used in photon beam radiation therapy, which go through the body and expose tissues to radiation both before and after they hit the tumor.

This echoes what was told to me by my Mayo urologist, Mayo R/O, Mayo PCP, and UFHPTI R/O.

Proton has only been around since about 2006 and very few long ranges studies done comparing both. Many short term studies have been done. What my UFHPTI told me his research (UFHPTI is the institution that got 25 million dollar grant to do a long term study of proton and radiation treatments) was showing the same conclusions that proton and photon success rates are identical.

Where the differ is the side affects and damage to other organs and tissues. The reason (again my UFHPTI R/O when I commented on so many children here) proton is used so much on children is they life span is so much longer than and adult and thus secondary cancers caused by radiation can occur during their life span.

My UFHPTI also told me (he has been doing proton for 20 years) he does not like the high dose radiation as he is seeing sooner and additional side affects. My Mayo PCP who says he stays atop of recent studies stated the information is showing increased issues with side affects of the high dose limited number of days treatments.

My Mayo PCP was the one who stated why years ago he wanted me to continue getting PSA test even though past reocmmendation were for it to be optional. He said Mayo was seeing an increase in stage 4 prostate cancer. They did a study to see what may be causing such an increase and saw that when they changed making PSA optional they could see the shart increase of patient coming is with stage 4. Thus they changed their protocol. This is the real time information and studies I was referring to.

The radiation treatments have greatly changed and improved. Even in the 2.5 years on MCC I have seen new treatments.

I get monthly newsletters from Mayo. They are citing studies now showing great promise for using a type of protein type chemical which only attach to specific prostate cancer cells and keeps them from multiplying and growing, and eventually dying. That will be great news if pans out in clinical trial as it will drastically change prostate cancer treatments.

I won't probably be around when that is offered but hopefully those of us in the future that will get prostate cancer wil not even have to deal with radiation damage.