Repeat radiation depends on the type you had the first time. According to my radiation oncologist, I'd be allowed to have radiation to the same spot in my spine a second time if I ever needed it.

That's interesting about the prostate sometimes repairing itself after radiation. Maybe just low doses or highly-focussed radiation (like proton beam)? And presumably, a self-repaired prostate would be easier to remove, since it would no longer be hard and rubbery, no? I still have only dry orgasms, which suggests to me that my prostate hasn't repaired itself yet 3½ years after 60 gy of radiation, but I have no special expertise to evaluate.