Many Prostate Cancers Missed: Study

Popular screening test may miss 82 percent of tumors

(HealthDay is the new name for HealthScoutNews.)

WEDNESDAY, July 23, 2003 (HealthDayNews) -- More than 80 percent of prostate cancers may be missed because the current threshold that specifies when to do a biopsy needs revision.

That's the contention of a Chicago doctor and researcher who has long pushed for changes in the way prostate cancer is detected.

Doctors order a biopsy to detect prostate cancer based on the results of a widely used screening test called a prostate-specific antigen (PSA) test. It detects blood levels of a protein produced by the prostate gland, a chestnut-sized gland surrounding the urethra, at the base of the bladder.

PSA levels are elevated in men with prostate cancer, but not all men with elevated levels have cancer. So there is ongoing debate about how much is too much. Many doctors use 4 nanograms per milliliter of blood as a cutoff and do a biopsy then.

But Dr. William J. Catalona, a co-author of the new study published in the July 24 issue of the New England Journal of Medicine, says up to 82 percent of cancers in men under age 60, and 65 percent of cancers in men aged 60 and above, may be missed using a threshold of 4.1.

A biopsy should be done when the PSA reading reaches 2.5, says Catalona, director of the Clinical Prostate Cancer Program at Northwestern Memorial Hospital and professor of urology at Northwestern University's Robert H. Lurie Comprehensive Cancer Center in Chicago.

"Even using the 2.5 [as a cutoff], there will be some cancers that have spread," Catalona says.

But not everyone agrees, including the author of an editorial that accompanies the study.

In the study, Catalona and his colleagues evaluated 6,691 men who underwent PSA-based screening between 1995 and 2001. Eleven percent, or 705 of the men, underwent biopsy of the prostate. Using a mathematical model, the researchers corrected for "verification bias," which arises when the presence or absence of prostate cancer has not been verified by prostate biopsy in every man screened.

And they concluded that if the threshold for undergoing biopsies is set at 4.1, 82 percent of cancers in younger men and 65 percent in older men would be missed.

About 220,900 new cases of prostate cancer will be diagnosed in the United States this year, according to American Cancer Society estimates, and nearly 29,000 men will die from it. While one man in six will contract prostate cancer in his lifetime, only one in 32 will die from it. Many die with prostate cancer, but the cause of death is something else, such as a heart attack.

In his own practice, says Catalona, he has been following the 2.5 cutoff for eight years and is confident it makes a difference.

"If your PSA is 2.5, get a biopsy, no matter what your age," he says. There's one exception, he adds. "There are a lot of men whose PSA will jump up because of inflammation in the prostate. Try a course of antibiotics first. If it doesn't come down, then ask for a biopsy."

Catalona is not without his critics. Dr. Fritz H. Schroder of the Erasmus Medical Center in Rotterdam, the Netherlands, writes in the editorial that "this recommendation is not ready for routine clinical practice" and calls for ongoing, randomized studies.

Dr. Herman Kattlove, a medical editor and spokesman for the American Cancer Society, says, "I think you would find a lot more prostate cancer if you biopsy at 2.5. But I am not sure it would be necessary to treat all of them." The cancer may be small, slow-growing, or both, he says. And the side effects of treatment, including incontinence and impotence, must be weighed against the benefits, he says.

If a man's PSA reaches 2.5, Kattlove recommends that he keep an eye on it. "See if it rises."

More information

To learn more about prostate cancer, visit the National Prostate Cancer Coalition and the National Cancer Institute.

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