"Advance" in PSA test challenged by Hutch research

An effort to improve a widely used test for prostate cancer is probably not very useful, local researchers have found.

The "PSA velocity" calculation, which looks at changes in concentrations of a prostate-gland secretion over time, can be affected by age, race, diet and even calcium supplements, researchers from the Fred Hutchinson Cancer Research Center in Seattle reported today.

Relying on the velocity calculations could lead to unnecessary biopsies — testing tissue from the prostate — and stress for the patient, said Dr. Alan Kristal, lead scientist in the study, published today in the online version of the journal Cancer.

The velocity test had been an attempt to make better sense of the commonly used PSA test, which has already been shown to have problems.

"This is not going to be the solution. It's not going to save the whole screening process from the problems of PSA," Kristal said.

Prostate cancer is the most lethal form of cancer for men nationwide, according to the American Cancer Society. About 30,350 will die of the disease this year, including 720 in Washington, according to the society. More than 232,000 new cases will be reported, including 5,510 in this state, the society estimates.

Experts recommend that men begin receiving yearly prostate-cancer screenings at age 50. That includes a rectal exam and a test for PSA, which stands for "prostate specific antigen," a protein that leaks into the bloodstream when cancer is present or when the gland is enlarged for other reasons.

But studies have shown the PSA test is not always reliable. A 2004 study by "The Hutch," for example, showed that about 15 percent of men age 62 to 91 who had normal PSA readings were later found to have prostate cancer.

In response to the research, some physicians turned to the PSA velocity calculations for help. In that method, doctors look at increases in PSA readings over time. PSA naturally increases as men age, and researchers thought an increase in the rate of change might be cause for concern.

For the study reported today, Kristal and his colleagues from the Hutchinson Center and the University of Texas analyzed six years of PSA test results from 3,341 cancer-free men, ages 50 to 74, in the U.S. They found that several factors could make the rate of increase go up or down.

The PSA velocity decreased with age but increased with a high-calorie diet. African Americans, who have a higher risk of prostate cancer, had nearly twice the PSA velocity as whites. It was lower among men who took high-dose calcium supplements, and among smokers.

Big fluctuations in a patient's weight also influenced PSA velocity: Men who gained weight had a lower velocity, and those who lost weight had a higher rate.

"My interpretation of this is that velocity doesn't tell you any more than looking at the patient's last test," said Kristal.

Warren King: 206-464-2247 or wking@seattletimes.com