@melvinw Ultrasensitive PSA is medically meaningful in my specific situation (stage 4b, currently fully suppressed with ADT+Erleada):

< 0.01 (not detectable) means anything borderline that shows up in scans doesn't require too much additional investigation, beyond some follow-up scans to ensure it's not changing

>0.01 (detectable) could trigger biopsies or other more invasive tests for a borderline imaging result (or in the case of my thoracic spine, precautionary radiation, since the spinal fusion means it can't be biopsied).

My original cancer was very aggressive — I went from a twinge in my back to paraplegic in about 5 weeks — so I don't necessarily have the luxury to wait and see if something starts growing again.

I also recognise that my case is atypical (my original oncologist told me only about 5% of prostate cancer behaves like mine did).

Agreed that once it's detectable, it doesn't matter much whether it's 0.02 or 0.05.