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The role of PSA today (in prostate cancer diagnosis)

Posted Sep 17 2008 1:32am
Before reading the text below, you may find it helpful to watch a brief video on how the results of your digital rectal examination and (more particularly) your PSA test(s) affect whether you should have a prostate biopsy. You can then come back to read the full information on this page.

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The results of prostate specific antigen (PSA) tests have two roles in the overall management of prostate cancer:

  • They can help you and your doctor to know whether you are at risk for prostate cancer (and therefore whether you should have a prostate biopsy in order to actually know whether your risk is real) and
  • They provide highly reliable information about “biochemical recurrence” of disease after definitive types of treatment.

In this section of The “New” Prostate Cancer InfoLink we are going to deal with the first of these two roles. We will deal with the second role on several other pages as they develop.

What is a “Normal” PSA Level?

In the early years of PSA testing (back in the early 1990s), it was generally believed that a “normal” PSA level was anything between 0 and 4 ng/mL. Data available at that time suggested that men were at very little risk for any prostate disease (prostate cancer included) unless their PSA level was greater than 4 ng/mL.

In hindsight this was clearly not a very wise belief — but then hindsight is always 20/20, right!

By the mid to late 1990s, Catalona and others were arguing strongly that any man with a PSA level of >2.5 ng/mL was at potential risk for prostate cancer, and the evidence was accumulating to support this position.

And now we know that PSA levels on their own are simply not good indicators of immediate prostate cancer risk. Men have been diagnosed who had virtually zero PSA levels as well as the more common levels anywhere above 2.5 ng/mL. So here is the answer to the question, “What is a normal PSA level?” … “There’s no such thing!”

So What DOES a PSA Level Tell Your Doctor Today?

Good question!

It is possible that, if you are relatively young, between about 35 and 50, your PSA level may be able to tell your doctor one thing absolutely on its own. We’ll get to that below.

However, your PSA level, or better still your PSA levels over time, when taken in combination with other available clinical data, including any signs or symptoms you may experience, can tell your doctor a number of things in the short term:

  • If it is very low (below, say, 0.5 ng/mL) it can tell him that your risk from prostate cancer is low. Your risk is not zero, but it is much lower than the risk for a man whose PSA is, say, 3.0 ng/mL or higher.
  • If it is increasing slowly over time, then it tells him you are at increasing risk for a prostate disorder, including prostate cancer, but a rising PSA is not a definitive indicator for prostate cancer on its own.
  • If it is increasing rapidly, then you are at significant risk for a prostate disorder, most likely to be either severe prostatitis or prostate cancer, and you need a full evaluation.
  • And if it is high (say 3.0 ng/mL or more), then you are also at significant risk for prostate cancer, and you may want to discuss a biopsy with your doctor.

Having said that, however, no PSA level on its own is a definitive indicator for a biopsy. It is only one of several possible risk indicators that your doctor will likely take into account in making a recommendation to you about next steps. A relatively new online “calculator” uses PSA and DRE data combined with other information to project risk for prostate cancer and the need for a patient discuss the value of a prostate biopsy with his physicians.

PSA and Long-Term Risk for Prostate Cancer

There are evolving data to suggest that a single PSA test result, for men in early middle age (between about 35 and 50 years old) may — let us emphasize that again — may be an indicator for long-term risk for prostate cancer (for up to 25 years later). We have discussed this in detail on another page.

It will probably be several years before definitive information about the accuracy of PSA as an indicator of long-term risk for prostate cancer can be established (or proven to be false). In the meantime, however, younger men may have nothing to lose by getting an early PSA test to establish a baseline PSA level. However, it would probably be very unwise to act on such a PSA test result by getting a biopsy unless there were very clear suggestions that indicated other forms of risk for prostate cancer too (e.g., a significant family history of the disease).

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