You asked a very narrow question....does your first post-RP PSA predict your case future.
It won't, but there are tools (nanograms) which use your other important case characteristics to predict your case outcome. Go to this MSKCC site and try the "Post-RP" tool. You'll see the importance of those other characteristics.
But starting with your low PSA is always a good starting point..
/www.mskcc.org/nomograms/prostate