PSA test not a predictor of prostate cancer

If, like me, you are a male past the age of 50 there’s a good chance you have a blood test called PSA (prostate-specific antigen) run once a year as an early warning for prostate cancer. But is this test of any value after all?

According to an article published in the Journal of Urology last October, serum PSA only reflects the size of the prostate, not the presence of cancer (J Urol 2004 Oct; 172 (4 Pt 1):

The article is discussed and explained in plain English in the online medical news service Medscape. Find it at (requires free registration).

It appears that studies performed 20 years ago showed a strong correlation between PSA and the presence of prostate cancer. However, newer studies have failed to confirm this finding. Lead investigator Dr. Stamey explains that the reasons for this change are not entirely clear, but the facts as they are understood today are that a PSA between 2 and 10 and, in many cases, between 2 and 20 is unrelated to the presence of cancer.’

Since the prostate is known to enlarge with age, many men will see their PSA levels climb over time. What makes things confusing is that when people with a high PSA go in for a biopsy most of the time they are diagnosed with cancer. So does high PSA mean you have cancer or not?

Dr. Stamey’s next statement clarifies this point: ‘If you biopsy men’s prostates, you’re going to find cancer, because we all have age-related prostate cancer. It begins in 8% of men in their 20’s, based on a study of men dying accidentally on the streets of Detroit. It rises to 70% of men in their 70’s.’

So here’s what seems to be happening: if you have an elevated PSA you will be referred for a biopsy and will probably be diagnosed with cancer. However, men of your same age with a normal PSA have the same likelihood of having prostate cancer.

Now isn’t prostate cancer something we want to have treated as soon as possible? Maybe not. According to Dr. Stamey’s research, while almost every man gets prostate cancer sooner or later only 226 per 100,000 over 65 die of this disease. That’s one quarter of 1 percent! It may be that this is a cancer we’re better off living with than treating. Let’s stay tuned.

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