There is a need to develop new biomarkers for prostate cancer beyond PSA, Scherr said. "Should a man when he turns 50 have a biopsy?" he said. "It is certainly an important question that needs being looked at."
But the study merely "makes a statistical point about an unusual population," said Andrew Vickers, a statistician whose title at Memorial Sloan-Kettering Cancer Center in New York is attending research methodologist.
"It apples to men who have regular screening," Vickers said. "It doesn't apply to men who haven't been screened. For those men, the PSA test might be more accurate."
And the study is misleading because of information it doesn't contain, said Dr. Ian M. Thompson, chairman of urology at the University of Texas Health Science Center at San Antonio.
The study includes only men on whom biopsies were done, Thompson said. "If you don't biopsy something, you don't know if you have cancer or not," he said. "The study is informative only of men who had biopsies. There is nothing in it about the criteria they used to recommend biopsies."
Risk factors for prostate cancer, such as ethnicity, age and family history, are not mentioned in the study, Thompson added. "You don't know anything about the people in their practice who never had a biopsy," he noted.
The PSA test has flaws, Thompson acknowledged. Most notably, it is unable to distinguish between prostate cancers that will grow so slowly that they do not endanger life and those that are aggressive enough to kill.
"But of all the tools we currently have, the PSA test is valuable," he said. "People dealing with other kinds of cancer wish they had a blood test like PSA."
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