zufas, you are exactly right on this question. It's an educated crap shoot at best. The remaining cancer cells don't glow in the dark, no current means of testing to show location. In my own situation, due to sharp PSA velocity both pre and post surgery, my own radiation oncologist puts the odds of my salvage radiation working in the 30-40% range. I don't like those odds, but willing to gamble and hope for once in the Game of PC that I can be on the "good" side of percentages. If it doesn't work, at least I know I tried. Now what this doctor did do, was to study my pelvic bed from a large number of scans, and studied my surgical notes in great detail, and with the IMRT planning, tried to recreate exactly where my prostate was extracted and based on that, tried to concentrate where the one itsy bitsy tiny positive margin was noted. She showed me on the radiation machine, how it creates a 3-d zap of my non-existing prostate gland. Will it work, jury is out for now. I am only halfway through my treatments, and always dealing with unpleasant side effects.
The point: we need much more advance testing tools. Things that don't even exist currently.
Age: 57, 56 dx, PSA: 7/07 5.8, 7/08 12.3, 9/08 14.5, 10/08 16.3
3rd Biopsy: 9/08 - 7/7 Positive, 40-90% Cancer, Gleason 4+3
Open RP: 11/08, Rht nerves saved, 4 days in hospt, on catheters for 63 days, 5th one out 1/09
Path Rpt: Gleason 3+4, pT2c, 42g, 20% cancer, 1 pos margin
Post Surgery PSA: 2/09 .05,5/09 .1, 6/09 .11. 8/09 .16
Latest: 7/9 met 2 rad. oncl, 7/9 cath #6 - blockage, 8/9 2nd corr surgery, 8/9 cath #7 out 38 days, 9/9 - met 3rd rad. oncl., mapped 9/9, 10/1 - 3rd corr. surgery - SP cath/hard dialation, 10/5 - began IMRT SRT - 39 sessions/72 gys.