Isaacs and Partin: Hoping to reduce unnecessary biopsies.
As wonderful and life-saving as the PSA test has been in detecting prostate cancer early, urologists and patients have wrestled with it, because many men with an elevated PSA have negative biopsies, may not have cancer, and shouldn't have to be subjected to repeated biopsies. Other conditions, including benign enlargement (BPH), can raise a man's PSA; it is far from being a purely cancer-specific blood test.
" We urgently need a marker that is
truly negative when cancer does
This is why Alan Partin, M.D., Ph.D., Urologist-in-Chief, has worked so hard to find and evaluate a better test. "We urgently need a marker for prostate cancer that's more specific; in other words, a test that is truly negative when cancer does not exist," he says. Recent studies in the U.S and Europe have identified genes that are found in prostate cancer cells but not in normal prostate cells. Among them is a messenger RNA called PCA3, a particular form of RNA, which was discovered and first reported in 1999 by Brady scientists William Isaacs, Ph.D., the William Thomas Gerrard, Mario Anthony Duhon and Jennifer and John Chalsty Professor of Urology; Marion Bussemakers, Ph.D.; and Jack Schalken, Ph.D.
"PCA3 is highly expressed in prostate tumors, but not in normal or BPH prostate tissue," says Partin. "Over the last decade, the work of these Brady investigators, in conjunction with scientists from other academic institutes and industrial collaborators in Canada and the United States, has provided us with a reliable urine test for prostate cancer that has great clinical promise."
In early trials, the PCA3 urine test proved able to detect prostate cancer nearly 70 percent of the time. Importantly, it also had a "negative predictive value" — which means it accurately reported that cancer was not present — of 90 percent. "This test has great potential to reduce the number of unnecessary invasive diagnostic procedures done each year," says Partin. "It has also shown some ability to discriminate among men who would benefit from a second biopsy, when a first biopsy showed no evidence of cancer."
"Although these initial results are very promising, further validation is necessary and under way to understand fully the clinical usefulness of this test," adds Partin. His research group is participating in an National Cancer Institute funded, multi institutional clinical trial of the PCA3 urine test. If the results from these and other studies live up to the biomarker's promise, the PCA3 test will be headed toward being approved by the Food and Drug Administration for widespread use.