PSA test for prostate cancer shown to have normal fluctuation

May 27, 2003

New York, N.Y., May 28, 2003 - A PSA (prostate specific antigen) blood test is part of routine prostate cancer screening for most men over 50. If the test result shows a moderately elevated PSA level, a referral for a biopsy is usually recommended. There is now evidence that suggests biopsy should not be performed until the test is repeated because PSA levels commonly fluctuate above and below the normal range.

In a study published in the May 28 Journal of the American Medical Association, researchers from Memorial Sloan-Kettering Cancer Center and colleagues studied nearly one thousand men who had five consecutive PSA tests over a four-year period. Up to one third of these men had elevated PSA levels; a finding which usually results in a referral for a prostate biopsy. However, subsequent testing of the same men a year or more later indicated that the PSA levels for half of the men had returned to normal. Had a biopsy been performed, it may have been unnecessary.

"A single, elevated PSA level does not automatically warrant a prostate biopsy," said Dr. James Eastham, a surgeon in the Department of Urology at Memorial Sloan-Kettering and the study's lead author. "We recommend having the findings confirmed by repeating the PSA test after waiting at least six weeks. Even if the repeat test shows an elevated level, prostate cancer will only be discovered in about one quarter of men who undergo biopsy."

The retrospective study looked at a population of 972 men with a median age of 62 years who participated in a national colon polyp prevention trial. These men were considered typical of the healthy male population at risk for developing prostate cancer, a disease that will be diagnosed in approximately 220,900 men this year. Annual blood samples were stored and later analyzed in order to study natural variations in PSA levels (serum prostate specific antigens circulating in the blood), a measurement frequently used in early detection programs for prostate cancer. Men who had five consecutive blood samples available over a four-year period were included in the study. While 21% had an elevated PSA (>4.0 ng/ml) at some time during the study, the level subsequently returned to normal spontaneously in nearly one half of the men and remained normal for most of them on further tests. A prostate biopsy of these men would not have been necessary.

"These natural variations in PSA detract from its use as a screening tool," said Colin Begg, Ph.D., chairman of the Department of Epidemiology and Biostatistics at Memorial Sloan-Kettering and senior author of the study. "A policy of confirming newly elevated PSA levels several weeks later may reduce the number of unnecessary procedures as well as the number of men diagnosed with a small, incidental tumor that poses no threat to life or health."

Waiting to confirm the diagnosis will not have an adverse affect on those men who actually have prostate cancer, according to Peter Scardino, MD, chairman of the Department of Urology at Memorial Sloan-Kettering. "A delay in diagnosis of a few weeks or months is unlikely to alter treatment efficacy," said Dr. Scardino.
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The study co-authors include Ellyn Riedel, M.A., Moshe Shike, M.D., Martin Fleisher, Ph.D., and Liane Litkany of Memorial Sloan-Kettering; Arthur Schatzkin, M.D., DrPH and Elaine Lanza, Ph.D. of the National Cancer Institute; and the Polyp Prevention Trial Study Group. It was funded by grants from the National Cancer Institute and by CaPCURE, the Association for the Cure of Cancer of the Prostate. Memorial Sloan-Kettering Cancer Center is the world's oldest and largest institution devoted to prevention, patient care, research and education in cancer. Our scientists and clinicians generate innovative approaches to better understand, diagnose and treat cancer. Our specialists are leaders in biomedical research and in translating the latest research to advance the standard of cancer care worldwide.

Memorial Sloan Kettering Cancer Center

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