A new type of PSA blood test could spare up to 200,000 men a year the need for painful biopsies to determine if they have prostate cancer, doctors in a large national trial said yesterday.
The test, which received government approval in February, helps to distinguish between early-stage prostate cancers and benign conditions that should merely be watched.
"Medical science has come up with a more rational approach to screening for prostate cancer," said Dr. Alan Partin, a urologist at Johns Hopkins School of Medicine, one of seven medical centers involved in the study.
The research, reported in today's Journal of the American Medical Association, was led by Dr. William J. Catalona at the Washington University School of Medicine. It was done under a research grant from Hybritech Inc., a San Diego firm that makes the test.
The new screening tool is used in conjunction with conventional PSA tests, which measure a protein known as prostate-specific antigen that is elevated in men with both cancerous and benign conditions of the prostate.
To screen for prostate cancer, doctors perform digital rectal examinations along with PSA tests. Suspicion is raised when the prostate has a hard, granular feel and the PSA measures higher than 4 nanograms per milliliter of blood.
Doctors recognize, however, that results between 4 and 10 nanograms often signify nothing more than a harmless enlargement of the prostate gland. Careful not to miss anything, they often suggest follow-up biopsies -- even when the prostate gland feels normal.
Experience shows that 75 percent of the time, biopsies will prove negative for men whose PSA tests place them in a diagnostic gray zone.
The new test, which measures a protein known as "free PSA," should be used for men whose prostates feel normal and whose PSAs are indeterminate. Free PSA is a harmless protein is not bound to anything else in the bloodstream.
Doctors should recommend biopsies for men whose "free PSA" constitutes less than 25 percent of total PSA, the study concluded.
Such tests could eliminate the need for about a fifth of all prostate biopsies performed in the United States each year and save millions of health-care dollars, the researchers said. Biopsies cost about $1,200 a piece, while the new test runs about $65.
Partin warned that people should not rely solely on this test.
"If you have a 52-year-old man with three brothers and father with prostate cancer and PSA is 4.2, I don't care what his percentage of free-PSA is," Parton said. "He has a higher likelihood of prostate cancer and should get a biopsy."
African-Americans also have higher rates of prostate cancer. That, along with other risks, should be weighed when considering whether to have a biopsy, Partin said.