@clevelandguy
I have posted this before maybe you missed it. I have watched Dr. Carl Rossi’s presentation on the use of proton radiation.

If you watch the 2023 PCRI Video and see Dr. Carl Rossi talking about radiation you find some interesting things. For one he’s been doing Proton radiation treatments since 1994 when they built a building for the machine in San Diego. The first patient was the person that invented it, He lived to over 100. He has done Proton radiation on over 13,000 prostate cancer patients.
That video link is Starting at 3:38:45

Dr. Rossi did start using proton radiation in 1991, Before that machine was built.

I am also aware of these technical aspects of proton

Protons deposit most of their energy at the end of their path, a phenomenon called the Bragg peak, before stopping completely. This allows radiation oncologists to deliver a high dose of radiation directly to the tumor and then have the radiation cease, avoiding unnecessary exposure to healthy tissues.

Proton beams can be precisely shaped to conform to the exact contours of the prostate tumor, which is crucial for accurate cancer control and protecting nearby organs.

Using proton radiation after someone has had their lifetime amount of radiation involves a few things, and is not possible to do for everybody.

Location of Recurrence: If the cancer is strictly confined to the prostate, it is easier to treat. If it has spread to surrounding tissues that were also fully irradiated, it is more complex.

Dose Received Previously: The doctor will analyze the original radiation plan (\(doses\) and \(fractions\)).

Patient Health: The ability to tolerate further treatment, considering age and other factors.