If he can't get you an good explanation of the nature of those final remarks. I'd get to a well known treatment center for an evaluation of the current situation and some explanations of what your original treating doc left you with.

To my way of thinking, what he did or didn't do well at this point is secondary. Getting your health care on track and the situation clarified is the primary concern.

Hopefully your is PSA is stable and low and you can do this at your own time/schedule.

My salvage radiation was 39 shots, I forget the numbers but something like the first 29 ish were prostate bed and lymph node area that was sort of at risk. The last 10 ish were just the prostate bed. He may be saying either his equipment was not functioning as it should, or it's outdated equipment. Either way, that's something he should have told you going in.

"Is this the appropriate ' standard of care ?" I doubt it. That often hinges on "informed consent" if he didn't tell you before you were treated that he couldn't treat you effectively, informed consent wasn't really there. That's a personal opinion, I'm not a doc or a lawyer.

Was you PET negative? or were there locations identified? If suspicion was cast on the lymph nodes with that scan and he couldn't treat those and didn't tell you , yeah, that's pretty bad.

Best of Luck going forward!