@watsohj
You should be having a PSMA PET scan. The MRI may not find anything, but somethings creating that PSA.

Frequently the MRI does not show cancer, which is very aggressive inside the prostate. The only way to find it is to do a biopsy that covers a lot of the area left of the prostate, Or do a prostatectomy. I wouldn’t do anything until the PET scan is done.

Hopefully you’re not in Canada and can get this done since your PSA is so high. It is guaranteed to find whatever’s causing this problem..

It is possible that during focal therapy they only removed a small portion of your prostate. In that case rising to 4.2 may be just normal for your age. I’d want the pet scan though to prove it is normal.