True validity of prostate cancer tests questioned

Jul 11 2005

According to the American cancer society, more than 232,000 men will be diagnosed with prostate cancer this year, and about 30,000 will die of it.

In routine checks, around 75% of American men over 50 have had a PSA test, which is performed to detect the early stages of prostate cancer, in the hope that smaller tumors might be more curable.

Men have for years been told that if their PSA scores fell below a particular threshold that was normal, while high results could indicate cancer.

Recent research now suggests that interpreting a popular prostate cancer screening test is far more complicated than doctors once believed.

Ian Thompson, lead author of a the recent study, says there is no safe cutoff point, and the risk of cancer rises steadily along with PSA levels.

Thompson, who is chairman of urology at the University of Texas Health Science Center at San Antonio, says this makes it far more difficult for patients to know when to pursue more invasive follow-up tests.

Thompson says the PSA tests, unlike a pregnancy test, have no clear lines.

Gilbert Welch, a Dartmouth Medical School professor and author of Should I Be Tested for Cancer? says the PSA test has long been controversial, and it has never been proven that the procedure saves lives.

Welch says that prostate cancer is different from other malignancies, and certain prostate cancers grow very slowly, or not at all, and are relatively harmless.

The PSA apparently misses many cancers and leads some men to have biopsies they don't need, but experts say it has helped doctors find far more cases of cancer.

In his view,Welch says that although examining tumor cells under a microscope can give doctors an idea of which ones are the most aggressive, doctors can never really know which tumors need to be treated and which could be left alone.

He says for this very reason, an unknown number of men needlessly suffer side effects of treatment, which can include impotence, incontinence, pain and other complications.

Welch says that instead of finding more prostate cancers, doctors need to find the ones that really matter.

William Catalona, director of the clinical prostate cancer screening program at Northwestern Memorial Hospital in Chicago, says doctors might develop a way to more precisely assess a number of factors, such as age, race, family history and obesity, to create more individual risk assessments.

New ways to use the PSA, such as tracking how it changes over time are also being found by doctors.

Thompson is optimistic that his study will prompt discussions between men and their physicians in order that such an important decision is made after consideration, and it is an informed one.

The paper is published in the JAMA: The Journal of the American Medical Association.