Posted 12/21/2010 10:37 AM (GMT -7)
In This Together Wife said... ...They put him on antibiotics for a couple weeks. Seems to me that if the PSA goes down after antibiotics then it is not cancer. Am I right?
Hi there, CareBear,
In simple terms, you are "probably" correct. But, it may be useful to understand a little more about how the prostate works because in reality things might not be so simple . The total PSA test measures the amount of prostate-specific antigen (a protein) in the bloodstream, but it does not distinguish where the protein comes from, and there are several possible sources.
First , any normally sized, normally functioning prostate throws-off (into the bloodstream) a small amount of PSA. If the prostate gland grows in size, the increased prostate material will naturally throw-off a higher amount of PSA. This is basically the “entitlement” level, or a baseline amount, of PSA.
Second , if the prostate is infected, the inflammation will temporarily result in a higher rate of PSA production. Some infections can be difficult to “solve”, but most respond in a matter of weeks to Cipro or Leviquin. Generally, if there is a relatively rapid (within weeks) up or down movement of PSA result, it is likely from the contribution of PSA in the blood from an infection; and in particular any rapid downward movement of PSA is generally attributed to the treatment of a prostate infection.
Third , if the prostate cells start to differentiate (which is a natural result of aging, but occurs at different times and different rates for different people), then additional PSA is thrown-off into the bloodstream. Differentiation is, of course, the forming of pre-cancerous and then cancerous cells. Cancer cells are known to divide rapidly (although prostate cancer cells are generally much slower than almost all other cancers, but faster than normal cells), and so PSA increases from cancer would generally follow an exponential growth curve (albeit slow) if left un-checked. There are lifestyle changes which can slow, or in some cases even reverse, the growth rate of prostate cancer growth (measured via PSA), although different prostate cancers in different men respond differently. (click HERE for more info)
BPH is a condition which also causes increased production of PSA.
Also, you are probably already aware of other activities which result in a short-term surge in PSA into the bloodstream: bicycle/motorcycle riding (which massages the prostate), ejaculation, a DRE. All of these things should be avoided for several days before a PSA test so that the results are not artificially high inflated.
So the key point I wanted to make in responding to your question is hopefully now obvious: the possible PSA contributing factors I’ve listed here may be going on simultaneously . The PSA test does not distinguish where the PSA comes from.
Another important factor in your friend’s case which you probably already know is that biopsy tests can result in “false negatives”; that is, a 12-core sample may not find prostate cancer, even when cancer is present. Each core sample takes about 0.1% of a normal sized prostate, so a 12-core biopsy samples roughly 1% of the gland material. Prostate cancer tends to grow around a “focal point”, and is not distributed homogeneously throughout the gland. So it’s possible that prostate cancer exists but was not present in the 1% of material which was sampled.
hope this helps…
The short answer to your original question is: “probably.” Perhaps a little overkill in my response, but hopefully the details add value to others who might be in learning-mode...
edit : fix typos Post Edited (Casey59) : 12/21/2010 11:03:41 AM (GMT-7)