I doubt anyone here will have the answer you're looking for. The Urologist is probably the better source than the Radiologist - because of their particular practice areas. The Urologist can speak from his own practice experience, and from what he's learned through reading and research - but each of the specialists (Urologists) is different and their experiences are going to vary.
I'm about 4 months post-op and my last visit with the surgeon/Urologist was December 24th. My second post-op PSA test is being reported as "0.0". I asked the Urologist if he could tell me if the results were 0.01, 0.02, etc. He said, "No." The university (Northwestern in Chicago) reports only to the .0 (.1, .2, etc. levels, not further) because, he said, such differences were insignificant. He also told me that I shouldn't be too concerned if my test results showed a 0.2 - but that above that level he'd want to do some more investigation.
I asked, too, about the liklihood of cancer spreading/appearing elsewhere in my body as the result of the prostate cancer - and he said, given my history, and based upon his practice experience . . . that the chances of such a thing happening are probably no more than 5%. From his mouth to God's ears!
Each of us are different, so what looks good for you or me may look different for the next guy in line. If you're comfortable with your primary care physician and Urologist, maybe they're the team to continue to listen to. If you have some doubts about their abilities - maybe look around for others you have greater confidence in.
Age: 59 (58 at diagnosis - June, 2008)
April '08 PSA 4.8 ("free PSA" 7.9), up from 3.5 year prior
June '08 had biopsy, 2 days later told results positive but in less than 1% of sample
Developed sepsis 2 days post-biopsy, seriously ill in hospital for 3 days
Dr. recommended robotic removal using da Vinci
Northwestern Memorial Hospital, Chicago, IL
Dr. Robert Nadler, Urologist/Surgeon
Post-op Gleason's: 3+3, Tertiary 4
Bladder & Urethral: Free
Seminal vesicles: Not involved
Lymphatic/Vascular Invasion: Not involved
Tumor: T2c; Location: Bilateral; Volume: 20%
Catheter: Removed 12-days after surgery
Incontinent: Yes (getting better, though)
Combination of Cialis and MUSE (alprostadil) three times weekly started 9-27-08
Returned to work 9-29-08 (18-19 days post-op)
PSA test result, post-op, 10/08: 0.0; 12/08: 0.0