NCPA - National Center for Policy Analysis

PROSTATE BENCHMARK QUESTIONED

July 8, 2005

For the past two decades, prostate-specific antigen (PSA) tests have been the key to detecting prostate cancer. However, there is no clear "normal" level for a (PSA) test, says the Journal of the American Medical Association (JAMA); thus, the test misses many prostate cancers and frequently gives false positive results -- leading to risky and unnecessary additional tests and procedures, including surgery.

Furthermore, experts disagree over whether early stage prostate cancer needs to be treated or whether screening has decreased mortality from the disease.

A PSA test is a blood test for a substance produced by the prostate gland. There are other ways to check for prostate cancer, like a digital rectal exam, but using a benchmark of four nanograms of PSA per milliliter of blood, doctors are able to prescribe treatment. If results are above four, they advise a biopsy; but, experts claim that PSA can increase for other reasons and many men with low PSA levels can still have cancer.

  • While three-fourths of men over 50 are believed to have had their PSA levels checked, 15 percent of men with a PSA below 4 have prostate cancer.
  • It's true that the higher the PSA, the higher percentage of prostate cancers the test will catch, but there is no clear cutoff point at which a PSA test result should trigger the need for further medical tests.
  • Additionally, treatment holds many risks -- rectal injury, impotence and incontinence; about one in 100 men undergoing a radical prostatectomy may die.

Experts say this is the end of the PSA era; it measures little more than the size of the prostate.

Source: Laura Beil, "Prostate benchmark questioned," Dallas Morning News, July 6, 2005; based upon: Ian M. Thompson, MD et al. "Operating Characteristics of Prostate-Specific Antigen in Men With an Initial PSA Level of 3.0 ng/mL or Lower," Journal of the American Medical Association, July 6, 2005.

For JAMA study (subscription required):

http://jama.ama-assn.org/cgi/content/full/294/1/66

 

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