@beaquilter In case it's helpful, the LIBERTAS trial currently underway (for pausing ADT in folk who responded well to doublet therapy using Apalutamide) uses this as their criteria:

"…reached a prostate-specific antigen (PSA) level < 0.2 nanograms/millilitres (ng/mL) after 6 months of treatment with apalutamide and ADT combination therapy…"

Abiraterone (Zytiga) is not _quite_ the same as the -lutamides (though still extremely good, and much less costly), so there's a reasonable chance he would have met this trial's entry criteria for strong responders if he'd been on that regimen, and he pretty much hit the target even on Abiraterone. 💪
https://clinicaltrials.gov/study/NCT05884398