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The PSA Paradox

In the United States, aside from skin cancer, cancer of the prostate is the most common cancer in men. In 2007, roughly 219,000 American men were newly diagnosed with prostate cancer, and 27,000 died.

In 1986, the FDA (Food and Drug Administration) approved the PSA - prostate-specific antigen blood test - to screen for prostate cancer in men over age 50. Even now, more than 20 years later, we have no idea if the PSA helps or harms men. The whole area is rife with contradiction.

You would think the PSA is a great test:

1. Since 1990, deaths from prostate cancer have declined by 1% a year, which many believe to be due to early detection from the PSA test.

2. Most of the urologists I know praise the PSA, use it all the time, and have no idea what all the fuss is about.

3. A dozen of my male patients had their prostate cancer removed when PSA screening led to a positive biopsy. They're convinced the PSA saved their lives.

4. Prostate cancer either causes no symptoms or just slows down the urinary stream, just as in many healthy older men. So it's hard to tell it's there. By the time prostate cancer causes symptoms, it has often spread beyond the prostate. So if you could do it, early detection would be best.

Here's why the PSA is problematic:

1. The PSA is insensitive. If you have an abnormally high PSA, the chance you have cancer is only 20%. Most positive findings are due to inflammation or benign enlargement. Roughly 30% of those with cancer have a normal PSA. So many tests are falsely positive or falsely negative.

2. Studies show that men who have a high PSA but a negative biopsy ("false positives") have a high degree of anxiety. They worry about cancer for the next two years.

3. No scientific study shows that PSA saves lives. But no adequate scientific study has ever been done.

4. What science there is shows that doing a PSA in men over age 75 causes more harm than good. This is because prostate cancer in men over 75 grows so slowly that the vast majority die of something else before their prostate cancer becomes a serious problem.

5. Radical prostatectomy (removing the prostate) leaves two-thirds of men impotent or incontinent, unable to control their urine. Radiation therapy, the major alternative to surgery, works as well as removing the prostate but frequently leads to impotence, incontinence, and/or bleeding from the rectum.

6. If you minutely examine the prostates of a hundred 65-year-old men who died of causes unrelated to their prostates, you'll find small areas of cancer in fully half. This means that tiny islands of prostate cancer are normal in men who will never develop clinical symptoms of cancer. So if a prostate biopsy shows cancer, what does that mean? How many men with a positive biopsy but no symptoms go on to develop actual disease? No one knows.

Bottom line:

Most medical schools teach there is no effective screening test for prostate cancer. The U.S. Preventive Services Task Force (USPSTF) has concluded that the PSA "is associated with psychological harm, and its potential benefits remain uncertain."

Frankly, I'm not sure what to do. My bias is that prostate cancer is less common in men under age 65, but when it occurs, it's more serious and more likely to kill them. I suspect that false positive PSAs are less common in younger men, too. So I'm more inclined to order a PSA in men in their 50s and early 60s.

Men with a father or brother who had prostate cancer are at increased risk of developing the disease themselves. African-American men have twice the risk of Caucasians. One can make the case to screen men with increased risk. But no one knows.

Last updated Sun, Sep 7, 2008

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