A new test for prostate cancer that measures levels of prostate specific antigen (PSA) as well as six specific antibodies found in the blood of men with the disease was more sensitive and more specific than the conventional PSA test used today. These are the findings of a study by researchers at UCLA's Jonsson Comprehensive Cancer Center.
The test, called the A+PSA assay, also reduced the rate of false-positives, tests that indicate the presence of cancer when no disease is actually present, said Gang Zeng, an associate professor of urology, a Jonsson Cancer Center researcher and senior author of the study.
"This is a very promising new approach," said Zeng.
"Instead of using just one parameter, PSA, to test for prostate cancer, we use multiple parameters that can be measured in a single reaction," added Zeng.
The retrospective study used blood taken before surgery from 131 patients from UCLA, Japan and France with biopsy-confirmed prostate cancers and compared results to blood taken from 121 men with either BPH or prostatitis, an infection or inflammation of the prostate that increases PSA levels. The study focused on six specific prostate-cancer associated antigens - NY-ESO-1, SSX-2,4, XAGE-lb, AMACR, p90 and LEDGF - which are found predominantly in patients with prostate cancer and not in benign prostate conditions.
The A+PSA assay looked simultaneously for PSA and antibodies to the six prostate-cancer associated antigens in a single reaction test done in a laboratory, much like PSA is measured. The new test takes about two hours, again similar to the PSA test.
In the new test, sensitivity - the percentage of men with prostate cancer who were correctly identified as having a malignancy - was 79 percent compared to the 52 percent found in PSA testing. Specificity - the percentage of healthy men who were correctly identified as not having prostate cancer - was 84 percent compared to the 79 percent found when testing for PSA alone.
The rate of false-positives using conventional PSA testing is 21 percent. With the new A+PSA assay, the false-positive rate is 16 percent, Zeng said.
"Science has improved so much since the PSA test was developed and I think it's time for a more specific and sensitive test to be developed," said Zeng.
"I think we have a test that has great potential to improve the diagnosis of prostate cancer. I knew it would be better than the classic PSA test, but I was amazed at how much better it really was in this study," added Zeng.
The study appears in the peer-reviewed Journal of Translational Medicine.