Your surgeon will tell you when to come in for your PSA test…you should do what he says.
Most surgeons simply follow a “rule-of-thumb” which they have developed, but it is based on the science. What you are likely to get here are a bunch of responses which begin with, “Well, my surgeon said…” Maybe what you were looking for, maybe not.
If you are also interested in the science behind the “rule-of-thumb,” here’s an explanation I had previously posted in another thread:
There is a "science" behind the level of PSA decline after surgery...I'll explain how it works, but to answer your question there is no specific "normal psa 6 weeks out." It depends primarily on one's PSA prior to surgery...the starting point. Once the primary source of new PSA is removed (the prostate and seminal vesicles), then the PSA already in one's bloodstream naturally diminshes over time.
Studies have been performed which show a distribution of how fast PSA diminishes, but in most men the "half-life" of PSA in one's blood after RP is 2-3 days. So, if one's "starting point" at the time of surgery is 5 ng/mL (for example), and if one assumes a 3-day half-life, and if one assumes no additional source of PSA added into the bloodstream, then the PSA level would reduce like this:
5.0 ng/mL at time of surgery
2.5 ng/mL 3 days later
1.25 ng/mL 3 days later, 6 days after surgery
0.625 ng/mL 3 days later, 9 days after surgery
0.3125 ng/mL 3 days later, 12 days after surgery
0.15 ng/mL 3 days later, 15 days after surgery
0.08 ng/mL 3 days later, 18 days after surgery
0.04 ng/mL 3 days later, 21 days after surgery
etc., etc.
The rule-of-thumb is to wait a bit longer than it would take to naturally diminish before taking a measurement. The extra times allows for a bit of "margin" or variability, and largely assures that no more PSA exists in the bloodstream from the prostate itself.
Shorter answer...six weeks is most common.
Hope that helps…