PSA Blood Testing for Prostate Cancer
To Screen or Not To Screen

Prostate cancer is one of the most common cancers faced by men.  The Prostate Specific Antigen (PSA) blood test has been used since the 1980’s to try to detect this cancer at an earlier stage.  In recent years, however, the usefulness of this test has been called into question.

Doc, I’m here for my physical, and I want every test done.

As a family physician, I see a lot of different people for a lot of different problems.  But my most important job is disease prevention.  My advice starts out the same way for everybody – eat a good balanced diet, and get regular exercise.  (Please re-read this last sentence – it is more important than the rest of this article.)  Then I start thinking about screening tests, to look for early signs of cancer or other diseases in people without any symptoms.  This process takes a little more thought than just checking off every box on the lab form.

What makes a good screening test?

Not all tests are created equal.  Some do an excellent job of detecting disease, and some give information that is not very reliable.  And unreliable information can be worse than no information at all.  Here is a wish list for the perfect test:

• It’s free (well, OK, reasonably priced)
• It’s sensitive (nobody with the disease gets a normal result)
• It’s specific (nobody without the disease gets an abnormal result)
• It detects a disease early enough to make a difference

How does the PSA test measure up?

Not as well as we would have hoped, it turns out.  On the positive side, the blood test is reasonably priced, when compared to other tests, and does a decent job of detecting most prostate cancers.  However, it does have some drawbacks, and the simple act of getting the blood test does involve some risk.

How could getting a blood test hurt me?

One of the problems with the PSA test is that it is not very specific.  Only about 30% of men with an abnormal PSA will actually have cancer.  In order to tell whether there is or isn’t cancer present, most men with an abnormal PSA will end up getting a series of biopsies of the prostate.   This procedure is uncomfortable, but usually safe.  However, if we do enough of these biopsies, we will run into some problems with pain, bleeding, or infection.

Another problem with these false positive results is the anxiety that they cause.  For every case of cancer that we find, there are going to be a lot of men without cancer who are told that they might have it.  Though certainly not life-threatening, all that worrying does have health consequences.

Isn’t it a good thing to find cancer early?

Usually.  The trick is, in order for early detection to be helpful, we need to be able to do something to make a difference for that person.  With prostate cancer, it is not clear that early intervention really helps.

One fact to consider is that prostate cancer often grows very slowly.  It may take decades for the cancer to become life threatening, and in the meantime the man with the cancer may end up dying of other causes.  In this situation, we would not have done the man a favor by sending him to the operating room to get his prostate removed.  Several studies have been done to try to find out if PSA screening actually results in fewer deaths, and the results have been mixed and inconclusive.

What about prostate surgery?

Without a doubt, prostate surgery can help get rid of cancer.  But there are downsides as well.  Any surgery has some risk of complications like bleeding and infection, or problems with anesthesia.  These risks are usually not terribly high.  However, when the prostate is removed, about half the time men will become impotent, and a third of the time they will have trouble controlling their urine.  Many experts question whether a man’s quality of life would be better served by skipping the surgery and letting the cancer grow slowly.  The risks and the benefits need to be weighed carefully on an individual basis.

What do the experts say about PSA testing?

Depends on who you ask.  In Canada and in several European countries, the experts have recommended against doing this test.  The American Cancer Society and the American Urological Association both recommend PSA testing for men who have at least ten years life expectancy.  The U.S. Preventive Services Task Force (considered to be the most scientifically rigorous group) has found insufficient evidence to recommend that we do, or that we not do, PSA testing. 

So what’s the bottom line?

Talk to your doctor, and know some of the issues ahead of time.  Before you get the test done, you should be aware that the benefits of PSA screening are unproven, and that there are definite risks.  Between the two of you, you should be able to come to a decision you can live with.

Click to close window