- A review of 20 years' worth of tissue samples casts doubt
on the value of prostate-specific antigen (PSA) testing for prostate cancer,
a new study contends.
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- In fact, the resulting treatments that often follow a
worrisome PSA test result may do more harm than good, according to the
study by Stanford University researchers.
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- "I have here in my laboratory a 20-year collection
of thin sections that allow us to construct the extent of cancer in the
prostate," said lead study author Dr. Thomas A. Stamey, a professor
of urology at Stanford. "We can look at the relationship between PSA
levels and the size of the cancer.
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- "In the first five-year period, there was a 60 percent
relationship between the size of the cancer and the level of PSA. In the
last five years, that has fallen to 2 percent, which is why we say the
PSA era is over. We are no longer finding significant cancers by PSA screening,"
Stamey said.
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- A key word in that sentence is "significant."
Over the past decades, research has shown that "all men will get prostate
cancer if they live long enough," Stamey said. The incidence is 8
percent for men in their 20s, compared to 70 percent to 80 percent for
men in their 70s, he said.
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- Yet prostate cancer is rarely fatal, Stamey said, with
a death toll of only 226 per 100,000 men over the age of 60. In many cases,
it progresses so slowly that it poses no major danger.
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- Yet doing a biopsy to see whether cancer is present has
some risks, while treatment of prostate cancer by radiation or surgery
can cause major problems, such as impotence, he said.
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- As a result, "lots of the cancers we diagnose don't
need to be diagnosed. Far more men die with prostate cancer than of prostate
cancer," said Dr. Howard L. Parnes, chief of the prostate group in
the division of cancer prevention at the National Cancer Institute.
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- The Stanford study appears in the October issue of the
Journal of Urology.
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- Stamey said there was a strong correlation between a
high PSA level and prostate cancer 20 years ago because the test was usually
done only when a physician suspected cancer. Today, the test is usually
done as a matter of routine, he said. Since PSA production is related to
the size of the prostate, a high level usually is related to benign prostatic
hyperplasia, the harmless increase in prostate size that occurs with aging,
he said.
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- Another important thing to note about PSA screening,
Parnes said, is that "there is no magic threshold of PSA below which
you can be assured you do not have prostate cancer and none above which
a biopsy should automatically be performed."
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- Right now, he said, "the National Cancer Institute
does not have a position on prostate-cancer screening. We are conducting
studies to determine if prostate-cancer screening actually saves lives."
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- One such study has enrolled 75,000 men who are undergoing
regular PSA testing, to determine whether testing can reduce deaths from
prostate cancer. Results will be available "probably at least five
years from now," Parnes said.
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- Another study, started 10 years ago, is intended to tell
whether surgery provides a benefit over watchful waiting for men with high
PSA readings, he said. Again, results are not expected for several years.
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- Meanwhile, Parnes suggests a cautious approach to PSA
testing.
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- Often, the test is given because "the perception
of physicians is that patients think they are not good doctors if they
don't give the test," Parnes said. "What doctors should do is
to find the time to discuss the pros and cons of screening. A PSA test
should be done with the informed consent of the patient."
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- http://www.forbes.com/lifestyle/health/feeds/hscout/2004/09/13/hscout521170.html
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- For new research into bacteria as a possible cause of
prostate cancer, go to: http:www.rense.com/general53/acsaid.htm
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- Acid-Fast Bacteria
- Discovered In Prostate Cancer
- 2004 Alan R Cantwell, M.D.
- Los Angeles, CA
- alancantwell@sbcglobal.net
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