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A Fallible Prostate Cancer Test
New York Times, July 30, 2003
It seems hard to believe, but a widely used screening test for prostate cancer in men is probably missing a vast majority of tumors. An analysis published in The New England Journal of Medicine estimates that the test — known as the P.S.A. test — probably misses more than 80 percent of the cancers in men younger than 60 and almost two-thirds of the cancers in older men. This must come as a shock to great numbers of Americans who have been assuming, incorrectly, that the test is highly accurate. It has been administered to some 75 percent of all American men who are 50 or older. The test measures the amount of prostate-specific antigen in the blood; elevated P.S.A. often indicates the presence of cancer, although it can also rise for other reasons. For the most part, doctors have considered levels above 4 nanograms per milliliter of blood worrisome and have ordered biopsies to provide more definitive diagnoses. But the 4-nanogram level has always been somewhat arbitrary. What the new analysis suggests, based on statistical modeling, is that reducing the threshold of concern to 2.6 nanograms could double the cancer-detection rate in men younger than 60 without greatly increasing the false positive rate. Even so, that lower threshold would still miss almost two-thirds of the cancers in the under-60 group. Men are henceforth on notice that "passing" the prostate screening test is no guarantee that they are cancer-free. The new analysis will ratchet up the uncertainties in the already confusing field of prostate cancer screening. The deeper problem is that no one has yet demonstrated that finding prostate tumors early saves lives or improves health. There is currently no way to tell whether the tiny tumors detected are destined to become lethal or will never cause a medical problem. Yet once people know they have tiny tumors inside them, many patients panic and undergo surgery or radiation treatments that can have debilitating side effects, including impotence, incontinence and bowel dysfunction. The trade-offs are so uncertain that many expert groups have shied away from recommending widespread screening. They leave it to individual men and their doctors to make their own judgments. Copyright
© 2002 Global Action on Aging
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