Are you having radiation in addition ADT? Even with undetectable PSA you still need radiation to scramble the DNA of the remaining cancer cells and hopefully destroy them.
The nodal dissection indicates escape of cells and they are not always captured by the lymphatic system.
I’m sure you know this already - just saying it for the benefit of those uninitiated observers on the forum who may conclude that ADT alone “kills” PCa.
Best of luck,
Phil