👍Pro: proton RT is more focussed, so is less likely to cause irritation to your bladder and rectum.

👎Con: proton RT is more focussed, so is less likely to neutralise early, undetected cancer spread in your bladder and rectum.

There is no difference in overall survival between photon and proton, and most people who do get irritation with photon have it fade in a few months (I'm a rare exception, but still, it's not so bad).

So if your insurance will pay for photon but not proton, you really have to look hard at the costs and benefits of shelling out a lot of your own money.