Cancer is unpredictable. Not just micrometastases, but individual cells can hide out in your body for many years before they suddenly decide to start multiplying.

Unfortunately, current medical technology can't detect those, so what looks like a "new trajectory" is often just stuff that was already there creeping just above the detection threshold. So the only way to find out if it's there, as @jeffmarc mentioned, is to stop taking treatments to suppress growth (like ADT and ARSI) and see if anything grows.

But all of that said, there is some evidence from STAMPEDE and other studies that if advanced prostate cancer remains undetectable for 5 years, there's a strong chance of long-term suppression (they don't like to say "cure").

Best of luck with some challenging decisions.