Kamis, 26 Maret 2009

The PSA Test for Prostate Cancer

For over 20 years some health professionals have been recommending that men over 50, and men as young as 45 if they belong to a high-risk group, be screened for prostate cancer by means of a PSA test (see Human Biology 5th ed., table 18.4). The PSA test measures the level of prostate-specific antigen, a protein from prostate cells. An elevated serum PSA indicates that prostate cancer might be present, in which case the next step is a biopsy to determine for sure.

When the PSA test was first introduced in 1987, scientists thought it might lead to as much as a 50% reduction in prostate cancer deaths. But now it seems that it may not save lives after all. In a study of 77,000 U.S. men, the 10-year death rate from prostate cancer was the same in a group who had an annual PSA test for six years plus a digital rectal examination for four years, compared to a control group who were never tested over the same time period. The study may need to be continued out for another decade or so to determine whether the PSA test has any usefulness over the longer term, however.

How can a test that accurately detects prostate tumors not save lives? Apparently the answer is that most prostate cancers are so slow-growing that older men are likely to die of something else first, even if they do have a diagnosis of prostate cancer. For older men, skipping the PSA test altogether may someday be safe option.

By the way, a digital rectal examination is not some sort of digital readout. It's a physician’s gloved digit, or finger.

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