Sorry, didn't mean to overwhelm you!
So if you have a few pelvic lymph nodes that were tracer-avid (i.e., took up the PSMA tracer agent on the scan) but no visible mets out of the pelvic region in bones or organs, you have locally advanced staging. Technically it's Stage 4a, but is not Stage 4b which means distant mets.
I suspect what your onco meant was that some if not most consider the disease "incurable" once it escapes the prostate. Radiation to the pelvic areas showing cancer presence and areas in the pelvis that do not show disease but where it could be present at the cellular or micro-met level can be curative. But being declared "cured" means no detectable disease for a period of 10 years. That's a tough criterion to reach.
But as has been discussed here, because of these 2nd generation drugs the battlefield is being reshaped, so to speak. Dr Mark Scholz is one of the prominent oncologists who believes the disease can be cured these days as long as it is oligometastatic (less than 5 distant mets) or confined to the pelvis.
I am unsure what to make of the idea that you're incurable because radiation failed to kill all the cancer. I'd engage your onco and get him to explain things better.
For me to hear incurable from my doc means he thinks all other options are a wast of time . I’m looking at cryoablation Brachytherapy or salvage prostectomy but what’s the point if they don’t provide a cure.