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July 1, 2002 |
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Test may cause needless testing and treatment SEATTLE -- July 1, 2002 -- Using a computer model, researchers have estimated that a common test for prostate cancer may result in an overdiagnosis of cancer in a third of the white men and nearly half the black men diagnosed with prostate cancer each year. The model developed by a research team led by Dr. Ruth Etzioni of the Fred Hutchinson Cancer Research Center, Seattle, suggests that the recent surge in prostate cancer incidence includes men who would not have had their cancers detected or treated within their lifetimes were it not for the prostate specific antigen or PSA test. The researchers reported their findings in the July 3, 2002 issue of the Journal of the National Cancer Institute. "This information is of great importance because considerable morbidity (illness) can be associated with treatment for the disease," Etzioni said in a prepared statement. To estimate the extent of prostate cancer overdiagnosis that would have resulted in the incidence patterns observed from 1988 through 1998, Etzioni and her colleagues compared cancer registry data on observed prostate cancer incidence with a computer-based projection of the increase in incidence of prostate cancer that would have been expected in the absence of PSA testing. The computer model was based on a hypothetical population of 2 million men between the ages of 60 and 84. The authors found that among men who were 60 to 84 years old in 1988, the estimated rate of overdiagnosis as a result of PSA screening was approximately 29% for white men and 44% for black men. These rates were consistent with the observed prostate cancer incidence for this age group from 1988 to 1998. The U.S. Food and Drug Administration approved PSA testing in 1986 as a way to monitor prostate cancer progression. Use of the test for prostate cancer screening caught on and increased dramatically beginning in 1988, despite little evidence to support a benefit in prostate cancer mortality reduction. Concurrently, prostate cancer incidence increased sharply and had more than doubled by 1992 before going back down. This apparent surge in incidence prompted concern over prostate cancer overdiagnosis. In an accompanying editorial, Dr. Siu-Long Yao of Merck Research Laboratories, and Dr. Grace Lu-Yao, of HealthStat in Princeton, N.J., say that overdiagnosis could be even higher than what was estimated in this study if stricter criteria were used in the model. They add that, assuming that PSA screening is effective, overdiagnosis might be acceptable if not for the fact that many men diagnosed with prostate cancer by PSA testing would be subject to unnecessary biopsies and a substantial risk of side effects from treatment, even though they would not benefit from the treatment. They conclude that "the consequences of overdiagnosis for the individual patient may be formidable, and for those who choose to discuss the option of screening with their health care provider, the important possibility of overdiagnosis should not be underestimated or overlooked." |
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