PSA Test Has Shortcomings, Study Shows
Value of Prostate Cancer Test Has Eroded Over the Years, Researchers Say; More Biopsies on the Horizon?
March 10, 2008 -- The PSA test is no longer as useful as it once was as a screening tool for early prostate cancer in men who have normal prostate exams, a new study suggests.
Researchers conclude that changes in biopsy practices over the years have diminished the test's value in predicting prostate cancer.
PSA testing has been widely used for nearly two decades to screen for prostate cancer, and numerous studies have supported the use of the simple blood test as a predictive test for the cancer.
But most of this research on PSA screening was done in the early to mid 1990s, before major changes occurred in prostate biopsy practices.
Before this time, biopsies were rarely performed on men with PSA levels lower than 4, whereas today men with PSAs as low as 2.5 are biopsied. Changes in biopsy practices, including taking more core samples from the prostate, have also led to more cancers being found at earlier stages.
Suspecting that these changes might have changed the predictive value of PSA testing, researcher Douglas S. Scherr, MD, and colleagues from New York's Weill Medical College of Cornell University conducted a study designed to test the theory.
PSA, prostate-specific antigen, is given off by prostate cells. A rise in PSA could mean a prostate tumor is growing.
The problem is that not every man with a high PSA level has prostate cancer. And not every man with prostate cancer has a high PSA level.
"We've been finding at this institution and really nationally and internationally that even men with very low PSAs often have aggressive cancers and men with high PSAs don't have cancer at all," Scherr tells WebMD. "So it is clear that the predictive value of the PSA test is in question."
(If you or a loved one has gone through prostate cancer, what was your experience when going through screening? Share your thoughts with others on WebMD's Prostate Cancer: Support Group message board.)
PSA Over Time
Scherr and colleagues reviewed 1,607 patients who had prostate biopsies done at Cornell's New York Presbyterian Hospital between 1993 and 2005, dividing the patients into three groups based on when biopsies were performed (1993-1997, 1998-2001, and 2002-2005).