September 1, 2005 A new blood test is more reliable at finding prostate cancer in its early stages by detecting a protein marker in blood plasma. Doctors say the new test, now in clinical trials, will have an accuracy of 95 percent, better than the commonly used PSA, which signals abnormal prostate conditions rather than cancer.
Most men over age 50 are familiar with PSA testing, used to detect prostate cancer. But the test can sometimes miss cancer cases. Now a new test can find cancer earlier.
When James Foster discovered he had prostate cancer, his life barely missed a beat. Now a prostate cancer survivor, Foster says, "I don't think I was shocked. I truly was almost preparing for it." But finding out he had the disease wasn't easy or quick. Like many men his age, he experienced the problem of having elevated PSA test results that could mean any number of things.
Robert Getzenberg, a cancer biologist at Johns Hopkins School of Medicine in Baltimore, says, "A blood test of PSA is not really an accurate marker of prostate cancer, but really a marker of abnormal prostate conditions."
Cancer biologists now have a new blood test, currently in clinical trials, that's more reliable and accurate at finding the disease in its earliest stages. The new test identifies a protein marker in blood plasma, called early prostate cancer antigen -- or EPCA. When the marker appears in a blood test, it indicates a high probability of cancer, not just that something is wrong. Doctors say it's the best indicator yet of prostate cancer.
"If you have the EPCA marker in your blood, you almost certainly, higher than 95-percent chance, have prostate cancer," Getzenberg says -- promising new number that might help reduce the amount of prostate biopsies, a painful, invasive procedure to confirm cancer, and focus on men who are truly at risk.
BACKGROUND: In the first clinical study of a new blood protein associated with prostate cancer, researchers have found that the marker EPCA, or early prostate cancer antigen, can successfully detect prostate cancer in its earliest stages. The current technique for detecting prostate cancer prostate-specific antigen (PSA) testing, can sometimes indicate cancer when none is there. Prostate cancer is the most common type affecting American men, with about 232,090 new cases diagnosed in 2005.
WHAT IS THE PROSTATE: The prostate is a walnut-sized gland, located between the bladder and the penis and in front of the rectum. Its primary function is the production of seminal fluid, the milky substance that nourishes sperm.
WHAT IS PSA TESTING: PSA testing is one step in early identification of prostate tumors, combined with digital rectal examination. But PSA testing can miss some cancers, or produce a false positive (indicate a cancer that doesn't exist). Furthermore, a prostate biopsy is a very painful and unpleasant procedure, with 12 separate tissue extractions followed by a month of pain. The biopsy usually needs to be repeated each year after the first positive PSA result, even if the initial biopsy comes out negative. Of the 1.8 million biopsies performed annually, only 15 percent come out negative. Reducing the number of biopsies requires for an accurate diagnosis would bring welcome relief to many patients.
NEW BLOOD TEST: Researchers at Johns Hopkins measured the ECPA levels in 46 patients, including those with prostate cancer, bladder, colon and kidney cancer, spinal cord injury, and noncancerous prostate inflammation, as well as 16 healthy individuals. They found that EPCA levels were high in 11 of the 12 prostate cancer patients and low in all the healthy individuals. They estimate an accurate diagnosis rate of 94 percent. When coupled with standard PSA screening, the new blood test could help reduce the number of unnecessary biopsies and undetected prostate tumors. The ECPA test very specific to prostate cancer; it doesn't indicate other types of cancer or benign prostate conditions.
WHEN AVAILABLE: Larger clinical trials will be starting soon, and it is believed that the blood test will be generally available to medical practitioners in 2006.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.