They say a simple urine test that screens for the presence of four different RNA molecules accurately identified 80 percent of patients in a study who were later found to have prostate cancer, and was 61 percent effective in ruling out disease in other study participants.
This is far more accurate than the PSA blood test currently in use worldwide, which can accurately detect prostate cancer in men with the disease but which also identifies many men with enlarged prostate glands who do not develop cancer, researchers say. Even the newer PCA3 test, which screens for a molecule specific to prostate cancer and which is now in use both in the U.S. and Europe is less precise, they say.
Arul Chinnaiyan, M.D., Ph.D., director of the Michigan Center for Translational Pathology at the University of Michigan and colleagues developed the test based on their recent finding that gene fusions - pieces of chromosomes that trade places with each other, causing two genes to stick together - are common in prostate cancer, and that by overriding molecular switches that turn off excess growth, they may be the causative factor in some forms of the disease. In 2005 they identified a prostate-specific gene called TMPRSS2 which fuses with either ERG or ETV1, two genes known to be involved in several types of cancer. In 2007, they identified another five genes that fuse on to ERG or ETV1 to cause prostate cancer.
In the current study, researchers built upon the PCA3 test by screening for six additional biomarkers, including TMPRSS2:ERG as well as some molecules generally over-expressed in prostate cancer, and some which are over-expressed in specific cancer subtypes.
The combination of the four biomarkers achieved a specificity and positive predictive value of greater than 75 percent, which they found to be five percent better than use of a PCA3 test alone, he says. Specificity is the probability that a test indicates a negative result if a person does not have a disease, and the positive predictive value is the proportion of patients with positive test results who are correctly diagnosed.
MEDICA.de; Source: American Association for Cancer Research