Prostates, PSA-tests, and Cancer

Recent research has indicated that PSA tests for cancer may have considerable type I and type II errors.

The P.S.A. test "is just not as discriminating as we thought it was," said Dr. Michael J. Barry, a professor of medicine at Harvard Medical School.

As a result, many experts are suggesting that the P.S.A. not be the single focus of prostate cancer screening, but rather one piece in a puzzle with other risk factors.

... First Dr. Ian M. Thompson Jr., chief of urology at the University of Texas Health Science Center at San Antonio, published a paper in The New England Journal of Medicine reporting that biopsies found prostate cancer in as many as 15 percent of men with P.S.A. levels below 4.

Then Dr. Thomas Stamey, professor of urology at Stanford University School of Medicine, published a paper in The Journal of Urology saying that P.S.A. tests were virtually useless. In most men, P.S.A. levels of 2 to 10 are caused by nothing more than a harmless enlargement of the prostate that occurs when men age. But prostate cancer is so common that biopsies find prostate cancer in most middle-aged and older men if doctors look hard enough. So the results would be the same if doctors simply biopsied men age 50 and older than if they did a P.S.A. test first.

One word of warning from the article is that if PSA levels are rising, there may be cause for concern, even if the levels are less than 4.0, which is a standard cut-off [variable confidence interval?]

The other major point made in the article has been well-known for over 20 years.

... last month, Dr. Peter C. Albertsen of the University of Connecticut Health Center published a study in The Journal of the American Medical Association saying men with prostate cancers that do not look particularly aggressive under a microscope - the majority of men whose cancers are found with P.S.A. tests these days - can do perfectly well with no treatment for at least 20 years. All they need is to be monitored by a doctor to ensure that their P.S.A. levels are not shooting up.

It is interesting to see that this is still a view widely held among prostate oncologists.

h/t to BenS. Neither of us has prostate cancer, so far as I know.