Assay tests can vary from one lab to the next and is quite common to see different readings. It is always best to use the same lab and the same assay method. I don't remember but it seems to me that there are several different methods used.
I know the concern you have, but do your best to wait until you get another test result. Based on the percentages of cancer in the path report, your history of 8 years being undetectable, I am willing to bet that this next test will put you back to all the other results. A big zero.
Keep us informed.
You are beating back cancer, so hold your head up with dignity
Age 58 at Diagnosis
Oct 2006 - PSA 2.6 - DRE Normal
May 2008 - PSA 4.6 - DRE Normal / TRUS normal
July 2008 - Biopsy 4 of 12 Positive 5 - 30% Involved Bilateral w/PNI - Gleason (3+3)6 Stage T1C
Robotic Surgery Sept 18, 2008
Pathology October 1, 2008 - Gleason 7 (3+4) Staged pT2c NO MX - Gland 50 cc
Seminal Vesicles and Lymph Nodes clear
Positive Margins Right Posterior Lobe
PSA 5 week Oct 2008 <.05
3 month Jan 2009 .06
6 month Apr 2009 .06
9 month Jul 2009 .08