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Earlier Start, Stop for PSA Testing?

Prostate Cancer Screening May Start Earlier -- and Stop Sooner
By
WebMD Health News
Reviewed by Louise Chang, MD

May 22, 2008 -- Prostate cancer screening may start earlier in life -- and, for some lucky men, end sooner.

Two of the hottest controversies in PSA prostate cancer screening are the ongoing debates over when a man should start screening and when he should stop.

These are life-and-death questions. If he starts screening too late or stops too soon, a man risks dying of undetected prostate cancer. If he starts too soon or ends too early, he risks harm from unnecessary biopsies and treatments.

Two new studies reported at this week's meeting of the American Urological Association in Orlando, Fla., will either help settle these questions or add fuel to the fire.

One study shows that a single PSA test before age 40 can identify men with almost no chance of getting prostate cancer -- and men with very high odds of getting prostate cancer -- in the next 30 years.

Another study shows that if a man reaches age 75 with a very low PSA score (below 3 ng/mL), it's almost a sure bet he'll never die of prostate cancer.

Early PSA Test -- and Then No More?

Hans Lilja, MD, PhD, of New York's Memorial Sloan-Kettering Cancer Center, isn't totally disinterested in PSA testing. He holds patents for blood tests for free PSA and other prostate-cancer-related assays.

But Lilja's provocative title for his AUA presentation was "A single PSA predicts prostate cancer up to 30 years subsequently, even in men aged less than 40."

PSA is prostate-specific antigen. It's a molecule given off by all cells of the prostate gland. The normal prostate sheds PSA. It sheds even more PSA during a prostate infection. But PSA usually goes way up when a man has prostate cancer.

Lilja and colleagues have three hypotheses about PSA. The first is the widely held idea that whatever causes prostate cancer leads to premalignant changes in prostate cells and results in a rise in PSA. The second is that whatever causes prostate cancer directly leads to a rise in PSA. And their third hypothesis is that a rise in PSA itself is part of the cause of prostate cancer.

In their view, prostate cancer doesn't happen overnight. Instead, Lilja and colleagues see it as a process that begins many years before cancer is diagnosed. And a rise in PSA may signal that this process is under way.

"Our findings are highly important in that they identify this sort of marker signal exists before age 40," Lilja tells WebMD. "It is unique that we have a biomarker with such extensive delay between when a blood sample is drawn and a diagnosis -- and are able to associate this marker with disease."

Lilja and colleagues took advantage of a "natural experiment" -- 21,277 Swedish men aged 33 to 50 who gave blood from 1974 to 1986 as part of a heart study. PSA screening isn't widespread in Sweden, but cancer registries are. So the researchers were able to tell which men got prostate cancer and which didn't.

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