Dr. Jacek L. Mostwin, Medical Editor of the Johns Hopkins Prostate Bulletin, shares insights from this year’s American Urological Association Annual Meeting. His comments on PSA testing come from a recent issue of the Prostate Bulletin.
Dr. Mostwin writes: As you probably know, PSA, or prostate specific antigen, is a protein produced by cells within the prostate, and blood levels of PSA can be measured in the blood. While higher PSA blood levels are often noted in men with prostate cancer, PSA elevation is not specific for prostate cancer. That said, at present, an elevated PSA test value (4.0 ng/ml or higher) is the most common way that prostate cancer is detected in the United States.
At a press briefing to describe his interesting study, Hans Lilja, M.D., Ph.D., an attending research clinical chemist at Memorial Sloan-Kettering Cancer Center in New York, detailed how a single PSA test given to more than 21,000 men in their early 40s was highly predictive of their developing advanced prostate cancer 20 to 25 years later. More than 60% of advanced cancers (T3) that developed over a 25-year period were associated with PSA values in the 80th percentile or greater among men between the ages of 44 and 50. “It’s fascinating to realize that 20 to 25 years away from the baseline sample, this (PSA) biomarker is so informative,” Dr. Lilja told the assembled reporters.
Data for Dr. Lilja’s study came from archived blood samples that had been collected and stored in Malmö, Sweden between 1974 and 1986. By 2000, 161 men had developed advanced prostate cancer. Their PSA values were then compared with those of 500 age-matched controls. Small elevations in PSA increased the risk of developing advanced prostate cancer. By age 75, men whose PSA was 0.5 ng/ml at the time of sampling, years earlier, had a 2% likelihood of developing T3 prostate cancer. However, if the original PSA level was 2 ng/ml or higher, the risk of advanced cancer was 12%, a sixfold jump.
"PSA is highly controversial,” said Dr. Lilja, “but obviously a PSA test taken early in life, before the age of 50, has an undoubtedly high capacity to predict future risk of prostate cancer, and cancer of unquestionable significance.”
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What this study suggests supports what my Hopkins colleague, H. Ballentine Carter, M.D., has suggested previously, based on his own PSA studies. That is, that men should have a PSA test in their 40s. Based on that PSA reading, a man could be placed in a low- or high-risk group, which would then determine how frequently his PSA is monitored over the next two decades.
Bottom line advice: At present, men are urged to have their first PSA test at age 50 -- an age chosen randomly and based on no real science. "This study looked at the development of advanced disease that is threatening to a man’s life, and it could help predict this,” said Christopher L. Amling, M.D., Director, Division of Urology, UAB Hospital, Birmingham, Alabama, and moderator of the press conference. "There should be new guidelines on how we screen for prostate cancer. These guidelines may appear soon, and this study certainly supports that.”
