Prostate Cancer: PSA Change May Be Key to Risk
Researchers Say Tracking PSA Changes Indicates Who's at Risk of Dying When Cancer Returns
July 26, 2005 -- What's the risk of dying when prostate cancer comes back after treatment? Two new studies point to who's at high risk and who isn't.
A crucial difference, the two new studies suggest, is how fast blood levels of prostate-specific antigen (PSA) go up.
Anthony V. D'Amico, MD, PhD, chief of genitourinary radiation oncology at Brigham and Women's Hospital and Dana-Farber Cancer Institute, led a study of 358 men who underwent radiation therapy. His team looked at whether prediagnosis changes in PSA predicted a man's risk of dying from prostate cancer. The findings confirmed the results of an
"The best use of PSA is not to look at the number but to look at the trend over time," D'Amico tells WebMD.
Stephen J. Freedland, MD, clinical instructor in urology at Johns Hopkins University, led a team that gathered data on 379 men who underwent prostate surgery but had their cancer come back.
"These studies show that looking at changes in PSA are more important than a single value," Freedland tells WebMD. "One PSA result is like looking at a snapshot of a horse race and trying to determine who will win. Looking at snapshots over time gives you a better idea."
Both studies appear in the July 27 issue of The Journal of the American Medical Association.
PSA is a chemical marker on the outside of prostate cells. As prostate cancer cells increase in number, blood PSA levels rise.
But PSA levels in and of themselves aren't a reliable indicator of cancer. Blood levels of PSA go up for other reasons besides cancer. And very deadly prostate cancers can occur even at low PSA levels.
"There has been controversy over what is the best use of PSA as a screening tool and what is the best use of the test as a tool to guide treatment," D'Amico says.
Instead of simply testing once for PSA and deciding that it is "high" or "normal," D'Amico says it appears to be more useful to test at regular intervals. This gives a reading on PSA change -- what doctors call PSA velocity.