Lynne,
You've gotten a variety of responses so far. Let me help explain WHY one waits a while after surgery before testing for PSA...(this info from Dr Patrick Walsh's book, the "Bible" for surgery)
PSA has a half-life in the bloodstream of 2 or 3 days. So, if one's PSA level before surgery was 10 ng/mL, as an example, it would take seven half-lives before the PSA fell into the undetectable range (for standard PSA test) of less than 0.1 ng/ml.
Example:
* start, 10ng/mL
* 1st half-life, down to 5 ng/mL
* 2nd half-life, down to 2.5
* 3rd half-life, down to 1.25
* 4th half-life, down to 0.625
* 5th half-life, down to 0.3125
* 6th half-life, down to 0.15625
* 7th half-life, down to 0.078125; below detection limits (std PSA test)
For a 3-day half-life, the starting point of 10 ng/mL requires seven half-lives, or 21 days, to dissipate in the blood to below the detectable limit of the standard PSA test. Obviously, someone with a higher starting PSA would take longer. Also obvious would be that one more half-life of time would be required in the above example to drop below the detection of the Ultra-Sensitive detection limit of 0.04 ng/mL.
As another note of related, but only passing interest, the PSA test result of a man taken the day after RP surgery would be nearly identical to the PSA result before surgery, mistakenly leading one, perhaps, to believe that the surgery had done no good. The PSA simply has not yet had time to dissipate in the blood in this example.
To generally avoid dealing with the unnecessary stress of being concerned whether enough time has transpired for complete dissipation, Walsh recommends as a general rule waiting 8-12 weeks after surgery for the first PSA test...it should be at "rock bottom" at that point.
Added note; "rock bottom" is not "zero." The notion of zero PSA is a misnomer, and does not occur. It is simply low enough to be less than the detection limits of the testing methodology. Men who had nerves spared, for example, will have left behind a source of PSA...albeit a source for only a small amount, but one that could be something above the detection limits of a Ultra Sensitive PSA test. The trend is what is important. There is no such thing as zero PSA in a living, breathing man.
Hope this helps explain the "why" to wait for 8-12 weeks after surgery for a PSA test...
Post Edited (Casey59) : 1/28/2010 5:37:42 AM (GMT-7)