But a new study by researchers at Washington University School of Medicine in St. Louis shows that doctors who follow this rule may be missing many more cancers than previously thought. Researchers biopsied 332 men who had PSA levels between 2.6 and 4 and found that a surprising 22 percent of these men had prostate cancer. The findings are reported in the May 14 Journal of the American Medical Association.
"This is the first large study of men with PSA levels between 2.6 and 4," says lead author William Catalona, M.D., professor of surgery and head of the Division of Urologic Surgery at the School of Medicine. Catalona was the first to prove that PSA tests could screen for prostate cancer, the most common cancer in American men and the second most deadly. "We now think doctors should biopsy men with a PSA of 2.6 and above," he says.
The study underscores the need for yearly PSA tests, particularly for men over 50, Catalona says. A safe reading of 1 or 1.5 could easily rise to a suspicious reading of 2.6 or 3 in a year's time, he explains. "All it takes is a simple blood test," he says. "It's so easy, and it may prolong lives." Catalona says previous studies have hinted that the PSA cutoff needs to be lowered. In 1995, a study by Harvard researchers showed that men with PSA levels of 2.6 to 4 were six to nine times more likely to eventually develop prostate cancer compared with men with PSA levels below 1.
In May 1995, Catalona began recommending biopsies for all of his patients with PSA levels of 2.5 or higher. Out of 914 patients at the School of Medicine, 582 declined the biopsy, often because other doctors had told them that any reading under 4 was safe. "The cutoff of 4 is very well-established in the medical community, " Catalona says. "It will be very difficult to change that."
A lower cutoff may be particularly important for black men since they have a 40 percent higher incidence of prostate cancer, Catalona says. Black men are also more likely to develop prostate cancer at an earlier age and have advanced cancer at the time of diagnosis. They are also more likely to die from the disease.
Some researchers believe the standard cutoff of 4 already leads to too many needless biopsies, so they won't be enthusiastic about lowering the standard to 2.6. But Catalona says many biopsies of men with PSA levels between 2.6 and 4 can be avoided if doctors also take into account "free" PSA, the percentage of PSA that floats freely in the bloodstream. Both free PSA and total PSA can be measured in the same blood sample. If doctors limit biopsies to men whose free PSA is 27 percent or lower, they will eliminate 20 percent of needless biopsies, Catalona says.
The controversy surrounding PSA screening goes beyond cutoff levels - some researchers still aren't convinced that regular screening and early cancer detection saves lives. But Catalona believes early detection is important, and some men who forgo biopsies until their PSA level reaches 4 may be waiting too long. Seventeen percent of the cancers found in the study were harmless according to the standard medical definition. The rest - 83 percent - had the potential to eventually spread beyond the prostate and cause life-threatening complications if left untreated.
In 1996, there were more than 317,000 new cases of prostate cancer reported in the United States and more than 41,000 prostate cancer deaths.