I did ask about the same q to the UO. Their response was while it is difficult to perform RALP after radiation , they do perform it on case basis. Same question I asked RO their response was similar to yours. But yes for person like in my age group , in general RALP is first preferred option (per UO). Proton treatment in my case is not preferred because (a) there has been significant advancement on photon tech and precision is in micron level and (b) proton is offered with Medicare

My surgeon and radiation oncologist both said if you have radiation first RP is off the table.