By Laura Beil,The Dallas Morning News

DALLAS – A new study has found no clear “normal” level for a PSA test, a finding that is likely to add to growing uncertainty over one of the foundations of prostate cancer screening.

Doctors had once hoped that blood tests for prostate-specific antigen, or PSA, a substance made normally in a man’s prostate gland, could signal when the prostate had turned malignant.

Since the introduction of the PSA test two decades ago, most doctors have settled on a benchmark of 4 nanograms of PSA per milliliter of blood as the flashpoint for a PSA test. Results above that level, and many doctors advise a biopsy of the prostate.

But the number appears to have little meaning, according to the new study, published Wednesday in the Journal of the American Medical Association.

“Patients have been taught that PSA less than 4 is normal, above 4 is abnormal. That’s not true,” said Dr. Ian Thompson of the University of Texas Health Science Center at San Antonio.

The study is the latest in a series that questions the value of the test, which has become almost routine in most older men’s physical exams. About three-fourths of men over age 50 are believed to have had their PSA levels checked, although studies have not yet demonstrated that PSA screening has lowered prostate cancer mortality.

The prostate, a walnut-sized gland involved in the production of semen, makes PSA as part of its normal function.

In addition to a PSA test, doctors also check for prostate cancer with a digital rectal exam.

In an important paper last year, Thompson and his colleagues reported that 15 percent of men with a PSA hovering below 4 have prostate cancer. The new paper expands on that idea in more detail.

The researchers found that, when laid on a graph, prostate cancer occurs along a steady arc – the higher the PSA, the higher percentage of prostate cancers the test will catch.

But the new research found no clear cutoff point at which a PSA test result should trigger the need for further medical tests.

Set the bar too low, and too many men undergo unnecessary biopsies. Too high, and the test will miss most cancers.

Although PSA screening has long had skeptics, the debate among urologists reached a new pitch last fall, when Dr. Thomas Stamey of Stanford University Medical School – an early champion of the PSA – announced, “the PSA era is over in the United States.”

In a study published in the October 2004 the Journal of Urology, Stamey and his colleagues analyzed data from prostates taken over more than 20 years, and tracked the severity of the cancers to each man’s PSA level. The conclusion: as it has become increasingly used, the PSA test measures little more than the size of a man’s prostate.

A PSA test, Stamey said last week, “gets you into more trouble than it helps you.” A man’s prostate gland commonly becomes enlarged, and produces more PSA, for reasons that have nothing to do with cancer. And even when the prostate is cancerous, experts disagree on whether those tumors need to be caught and treated so early. Prostate cancer is a relatively common malignancy, but it is not always aggressive. Men with prostate cancer are more likely to die with their disease, not because of it.

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“Almost every man gets prostate cancer with aging,” Stamey said. “I know damn well at (age) 76 I’ve got at least a 70 to 80 percent chance of having prostate cancer.”

He says that knowledge doesn’t bother him because he understands something else probably will catch up with him long before a prostate problem will. And, according to the U.S. Preventive Services Task Force, treatment for prostate cancer runs a risk of rectal injury, impotence and incontinence. One man in 100 undergoing a radical prostatectomy may die.

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PSA screening “can diagnose a lot of guys who don’t need to be treated and don’t need to be cured,” said Otis Brawley of Emory University School of Medicine, who as former assistant director at the National Cancer Institute, helped design a large prostate cancer prevention study.

“This PSA screening frenzy,” Brawley said, “has taken us away from a real scientific question and real scientific problem – that is, how to distinguish the cancers that do need to be treated from the ones that don’t need to be treated.”

The dilemma for patients, he said, is not knowing on which side of that line their tumor falls.

Many urologists acknowledge that the PSA test has not become the precise tool doctors had once hoped. Some specialists have even called for cancer screening with the PSA test to be abandoned. Others, however, say that it can remain an important tool for cancer detection, but test results must be interpreted thoughtfully.

“It’s not just a lab report,” said Dr. Claus Roehrborn of the University of Texas Southwestern Medical Center at Dallas.

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Thompson, from San Antonio, believes that the test must be considered within an individual patient’s circumstances and interpreted in the context of age, family history and other risk factors for prostate cancer. “Rather than using a single value, you will integrate a man’s risk with the PSA,” he said.

Even the most fervent advocates of the test want to wean doctors away from a single-number fixation.

“Before, they were looking for a magic number. Kind of like a pregnancy test. But it’s not that simple,” said Dr. William Catalona of Northwestern University School of Medicine, and a pioneer in the development of the PSA test. Instead, he and many others now believe that doctors should pay attention to the dynamics of the PSA test results, watching how rapidly it rises rather than just whether it is above or below a predetermined point.

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Anthony McClure would agree. In January, the Highland Park, Texas, businessman got a call from Roehrborn, his urologist. McClure’s PSA level had jumped from 1.9 to 2.7 in just a year, and the physician took notice. A biopsy confirmed Roehrborn’s suspicions about cancer. McClure had his prostate removed in March.

“It would never have been detected without the PSA,” McClure said. He was aware of the potential side effects of treatment, and that he likely could have lived many more years without problems. But he is a relatively young man – only 62 – who lost his wife to breast cancer three years ago. He wanted to be through with cancer.

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Jerry Nabors of Wichita Falls, Texas, is having surgery Thursday, after a routine PSA test led to a biopsy and discovery of his prostate cancer. “If I were 65, 75, I’d say, “Let’s watchful wait,”‘ he said. But he is 56. His father is 92, and he hopes to share his family’s longevity, without worrying about cancer for the next three decades.

Nabors said he knows that a PSA test isn’t perfect, but credits it with finding his cancer. He hopes that scientists will soon turn up with a new blood test that holds all the promise that once surrounded the PSA.

“Until it’s replaced with something better,” Nabors said, “it’s what we have.”

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(c) 2005, The Dallas Morning News.

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AP-NY-07-05-05 1932EDT

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