In the U.S., nearly a quarter of a million men will be diagnosed with prostate cancer this year. The test most used to determine whether prostate cancer might be present is known as the prostate specific antigen (PSA) test. The PSA test uses a blood sample to check for elevated levels of an enzyme produced by the prostate but the PSA test is dogged by controversy. The main problem is that a high PSA level does not always indicate prostate cancer as PSA levels can vary quite dramatically between men. Many doctors believe that a rise in PSA is more significant than a consistently high PSA. Additionally, high PSA levels can also indicate non-cancerous prostate conditions such as benign prostatic hyperplasia (an enlarged prostate). But researchers from the University of Michigan (U-M) say they have now designed a new test which promises to be a much more accurate predictor of cancer than the PSA test. Details of the new test appear in the New England Journal of Medicine.
To design the new test, researchers looked at blood samples taken from prostate cancer patients prior to surgery, and from males with no history of cancer. They tested the samples against a library of bacteriophage organisms that express proteins on their surface, and were able to narrow the field to the 22 biomarkers (biological indicators) that most often pinpointed the cancerous blood samples. The researchers then used these 22 biomarkers as the basis of the new test. In analyzing the new test, the researchers found that non-cancerous samples were identified correctly 88 percent of the time and cancerous samples were correctly identified 82 percent of the time.
The researchers said that the new test proved to be more reliable at predicting cancer than PSA level, which relies on a single biomarker. PSA testing results in a false positive around 80 percent of the time, leading to unnecessary biopsies.
The researchers believe the new test may initially be used to fill the gap between a PSA test and a biopsy. "Initially, we envision this new test could be used as a supplement to PSA. A physician might suggest a patient with an elevated PSA have this test before a biopsy to better determine whether it's a cancerous or benign condition. In the future, I think this could replace PSA," said study author Arul Chinnaiyan, Professor of Pathology at the U-M Medical School.
The researchers now plan to conduct further studies to validate the findings with a larger group of patients.
