PSA isn't an indication of how aggressive or how extensive the cancer is.
Some prostate cancers produce lots of PSA into the blood stream, and some others (in particular some aggressive ones) lost the ability to produce PSA at all.
At the extremes, I've come across a couple of cases of PSA in the 600's which wasn't metastatic although this is very unusual at that level, and of course there are men with normal/low PSA who are metastatic.